Early-game Mutalisks are harassment units and should be used as such. They should only directly engage an army when they massively outnumber the opposing force. Their strength lies in their mobility, picking off stray units, workers and buildings. Because no unit is fast enough to keep up with Mutalisks, they provide indirect map control - If an enemy Terran splits up his forces to take the offensive, mutalisks can be used to pick off buildings and units within the Terran's base, forcing the enemy's forces back to defend.
Deciding how many Mutalisks to morph is crucial, especially against a Terran opponent. For example, five Mutalisks are required to destroy a Turret in five volleys from the entire group. Six Mutalisks kill a Turret in four shots, and eight Mutalisks do the same in three shots. It takes twelve Mutalisks to be able to kill the Turret in two shots (although eleven are sufficient to make it burn down soon after the second volley hits). Mutalisks are rather effective against most typical Anti-Air Defenses, as their armor classification is light and explosive attacks deal half damage (such as those from Hydralisks, Dragoons, Missile Turrets, Goliaths, Wraiths, Scouts, and Valkyries. [Though Valkyries are deadly to Mutalisks anyways, due to their splash damage.]) As each Mutalisk is added to the group, the benefits gained decrease. The number of Mutalisks to make depends on the situation and must be learned through experience.
Mutalisks can most efficiently harass when "Mutalisk Stacking" is used: a clump of Mutalisks that generally appears, moves, and attacks like a single Mutalisk. This makes it very difficult for an opponent to target-fire the weakest Mutalisk in the group. Also, with proper micro, every Mutalisk in the stack will attack at the same time, allowing the Mutalisks to dance in and out of the enemy's firing range, greatly reducing damage taken.
In order to stack Mutalisks, they must be grouped with a unit a sufficient distance away, which triggers the magic box to activate. There are several viable options: a Larva, Overlord, or burrowed/stuck unit that can't move.
The advantage of using a Larva is that it's unable to move, meaning there is no concern to whether your unit will move as well. The drawback, however, is that once it's morphed into an egg, the Larva is removed from the group. If this isn't noticed, the Mutalisks will become unstacked.
The Overlord is generally the best choice for stacking Mutalisks. The disadvantage is that the Overlord will also move to the points given to the entire selection group, so it may move into enemy territory, or in some cases move close enough to the group of Mutalisks to prevent stacking. Although there is the possibility of the Overlord flying into harm's way, losing an Overlord is much better than losing Mutalisks because they were unstacked and uncontrolled. Ideally, the Overlord nearing the enemy base is removed from the group and replaced with a new Overlord from the base. Be sure not to replace it with an Overlord that is purposely placed in a location for detection.
Another choice is to use a burrowed unit. The advantage to this is that a burrowed unit (usually a Zergling) in a safe spot will never move and won't be removed from the group. However, Burrow must be researched for this, and typically this is not used unless Burrow is already researched for another strategy.
A Zergling trapped behind a mineral line can also be used. A minor drawback to this method is that at least two Zerglings are needed to block one in, except on a map such as Medusa where it is possible to trap the Zergling by abusing the AI path finding.
A micro trick to make all Mutalisks pop at the same time is to shift select all nine larva and bind them to a hotkey. This way, when the Mutalisks pop they will remain assigned to the same hotkey and can be sent to the enemy base slightly faster.
Diagonal movements, as opposed to horizontal or vertical, are better for maintaining a Mutalisk stack. There is something strange in the StarCraft engine which makes Mutalisks behave as if they were in the magic box when they make short range horizontal or vertical movements. When Mutalisks move diagonally they will always stack together. This is one of the reasons that engaging diagonally is better than engaging horizontally or vertically and one of the reasons that the Chinese Triangle technique (see below) works.
To keep Mutalisks stacked, constant movement commands are required, since a group of stacked Mutalisks will fan out upon reaching a destination.
Please note that in rare cases, when no other unit is available (e.g. in a Use Map Settings map), the Mutalisks can be stacked by rapidly making them move, especially in a circle. Another way of stacking is rapid clicking on a Mineral Formation.
Now that your Mutalisks are clumped up as one, you want to make them fire at the same target. This is particularly true against Marines and workers - you want dead units. Dealing a bit of damage to all units does you no good.
Mutalisks have quite a range. Unfortunately, their AI is not very sophisticated so you rarely see it. If you attack-move a Mutalisk and let it acquire its own target, it will not find the target until it is in range, and then it will begin to decelerate and fire. This is why Mutalisks often appear to have a small firing range, while human-controlled Mutalisks seem to have double or triple the range. To avoid this problem you have to control your Mutalisks. Always give them a target; never leave them on stop, attack or hold position.
"I have a question. Sometimes I just tell the Mutas to hold behind a mineral line that is hard to defend, but they end up just sitting there, not attacking. Is it because they have been hit by a unit that is out of range? Any solutions?"
Yes, if there are enemy fighting units around, your Mutalisks will not attack any non-fighting units or buildings until those fighting units are out of range or dead. This is why giving Mutalisks targets is so important.
Never let your Mutalisks decelerate, as their relatively slow acceleration could mean big problems when an army comes near. This is why you will often see progamers dancing their Mutalisks at full speed when there is no harm in sight - in the event that an army is arriving, the Mutalisks will already be at top speed and can easily escape. You should practice keeping your Mutalisks mobile and giving them targets.
In this vein, Mutalisks can only shoot in the direction they are facing. If you tell a Mutalisk to attack-move behind it, it will decelerate, turn around, and fire - an unfavourable result. Mutalisks can, however, turn around without decelerating, meaning if you first tell the Mutalisk to turn around, and then give the attack command (or much easier, simply target a unit behind it), it will happen much quicker. Once you've mastered this, you can issue a turn around command, then the attack command (or target a unit behind your group), followed by another turn around command, which will result in your Mutalisk essentially flying at full speed while firing backwards!
Now that you have a feel for the above points, you need a feel for Mutalisks cooldown. Cooldown is the time a unit must wait after attacking to attack again. There's no way I can explain Mutalisks' cooldown length to you in a meaningful way. If I were to guess, I'd say it's about 0.7 seconds.
Now that you have a feel for their range, speed and cooldown, you can start practicing "sniping" units with Mutalisks. The technique is simple - fly grouped Mutalisks straight at their target. Some time before they are in range, issue the command to attack. As soon as you fire, retreat your Mutalisks back a ways and then turn around for a second attack. You want to time your second attack so that you are reengaging the enemy just as your cooldown ends, thus maximizing your damage. It takes practise. Also, it is better to err on the side of caution, i.e. waiting too long rather than not waiting long enough.
 Attack vs. Patrol vs. Hold Position
While Microing Mutalisks, there are various commands that you can issue to the Mutalisks, but their use varies depending on the situation.
- Attack (A + Click) - Pressing A and Clicking is the most natural way to Mutalisk Micro, and it is usually one of the most effective. This technique is most effective when you have enough Mutalisks to 1 shot a unit. As an example, when you have only 6 Mutalisks, it is better to target individual Marines since you need to kill one Marine for every volley. Another time when this technique is effective is when you are trying to specifically target something, whether it is a worker or a building, and you are getting shot at. The other types of micro don't work in this situation because the Mutalisks' AI want to fire at whatever is shooting at them, so manually targeting the unit or building is required. It is important to note that this is not an attack move. If you try to target the ground, then the Mutalisks' AI will take over, which is usually a bad idea.
- Hold Position - Against Marines and Medics, this is usually the most effective way to micro if you went for a 3 Hatchery Mutalisk build. The method is fairly simple, just move your Mutalisks in range of the enemy units, press 'H', and then retreat. The theory behind the Hold Position micro is that with 9 or more Mutalisks, that would be at least 81 damage in one volley. Therefore, if you fire at a single Marine with 9 Mutalisks, 41 damage is being wasted. Therefore, it is more efficient to spread the damage out to two or even three Marines. Another convenience of Hold Position micro is that the 'H' key can be reached by your left hand easily. Therefore, it feels very natural to use Hold Position micro.
- Patrol - Patrol is the least used method of the three in most situations because of the way it works. In general, patrol negates the need for a unit to decelerate and fire, but since the two methods above solve this problem easily, patrol is usually not seen. Therefore, you usually only use patrol when microing against Scourges, but it is important to note the benefits of Patrol micro as well. Patrol micro is similar to the Attack micro, but the difference here is that your Mutalisks will fire faster than with either Hold Position or Attack, and they will generally only attack one unit. Therefore, Patrol Micro is like a safer Attack Micro since if you misclick, then the Mutalisks will still fire, and it acts like a better Attack anyway. However, do note that you cannot target specific units with this micro.
 Chasing Fleeing Units
Like all units without firing animations, Mutalisks can attack while remaining at full movement speed. This is the origin of the term "dancing", although it has become diluted and is now usually applied to Dragoons. Simply issue the attack command followed instantly by the move command. One thing to note is if you do not give the Mutalisks a target, they often decelerate before firing. If you are chasing units that move at the same speed (Mutalisks, Corsairs, etc.) this will cause you to let them slowly get away. This is why you must target a unit rather than attack-moving.
 Dealing with Latency
Latency is the time between when you issue a command and your units react to the command. You will notice on LAN or Hamachi, units respond instantly to commands, while on Battle.net there are slight delays. Normally these slight delays are not an issue, but when trying to execute difficult Mutalisk targeting, you should alter your game play and strategy to account for latency.
Every command you issue has to be before you need to happen. This means if you are targeting Marines, you actually need to tell your Mutalisks to run away before they have fired. Getting the timing down with latency can be nearly impossible, meaning you should adjust your game accordingly in the following ways:
- Don't target Mutalisk-killing units.
Without latency, Mutalisks can easily target Marines in groups or even Archons. You would be wise not to attempt these manoeuvres with latency. For every time it works, I would wager it will end in disaster two or more times.
- Don't overdo your dancing
Although you should always try to keep your Mutalisks moving at full speed to avoid ambush, the presence of significant latency can make this tactic more risky and less advisable. When you're fighting a single Turret or a Cannon, just stay and kill it. When you find an undefended worker line, just sit there and target the Workers individually, rather than weaving in and out.
Remember that while your Mutalisks are alive they are dealing economic damage (you are expanding while he cannot move out) and also dealing psychological damage (frustration). Don't give this up trying to be a hero against a group of 24 Marines.
 Using Mutalisks vs. Zerg
 Dealing with Scourge
Depending on the latency and your skill level, there are a few different ways to handle Scourge. (see also the Mutalisk vs. Scourge Guide)
First, you never want to leave your Mutalisks idle in vision of enemy units, as this will allow your opponent to easily clone his Scourge against you. Ideally you want to be engaging the Scourge, forcing your opponent to try to clone them quickly, and increasing the chance that he commits an error.
That being said, Scourge lose their effectiveness as Mutalisk numbers increase - cloning them becomes difficult at high numbers and they are more likely to die from Mutalisks' bounce damage when moving in. If you find yourself ahead against a heavy Scourge user, you are better off building up your Mutalisks and engaging then.
When fighting an army of Mutalisks and Scourge, you want to bait the Scourge by engaging the Mutalisks. As soon as you see the Scourge approach, begin your retreat while focus firing backwards to eliminate the Scourge. Once they are gone, reengage the lone Mutalisks.
If you are getting chased by Scourge you have two options. The easiest is to try to figure out which Mutalisks are targeted by the Scourge, by sending them on different paths and seeing where the Scourge go. Once you know which Mutalisks aren't targeted, you can bring them back to fight while the targeted ones continue to run. Secondly, you can try the "Chinese Triangle". I'll try to explain it with words but it might not come across, I encourage you to watch the video in that link if you want more information. Assume your Mutalisks are running east. You want to tell them to move in three different directions, essentially drawing a triangle. The first will be a 90 degree turn, so either north or south in this case. Let's assume north. Your second click is back towards the direction you were heading, but 45 degrees past. So in this example, you were flying east, then went north, and then went southeast. Your final click is back towards the direction you were running from, west in the case. So the entire manoeuvre is E, N, SE, W. If you do this properly, and very quickly, the Scourge screw up and spin back, giving you time to snipe one and continue running.
There is some minor debate about attack-move versus patrol when fighting Scourge. The general consensus is that patrol works better if it is placed properly (close to your Mutalisk group). I personally always use attack-move.
If you are uncertain about your micro abilities but already gained an advantage against a Scourge user, simply amass Mutalisks before attacking rather than engaging with a low number of Mutalisks. Mutalisk against Scourge micro is among the hardest in StarCraft, and the latency of Battle.net does not make it any easier.
Upgrades are a difficult part of Zerg play. First off, in Mutalisk versus Mutalisk battles, Carapace is always the best upgrade to get. If you can afford it, three carapace upgrades before any attack upgrades is preferred. When a Mutalisk fires, its damage is divided by 3 every bounce. So the first hit would do 9 damage, then bounce to another target and do 3 damage to that target, bounce and do 1, etc.. When you upgrade attack, this becomes 10, 3.33, 1.11, essentially an increase of 1.44 damage; however, when fighting an opponent who instead upgraded carapace, each of those hits gets reduced by 1, meaning it would become 9, 2.33, 0.11. The carapace-upgrade Mutalisks are taking 1.56 less damage per attack. If you don't understand, upgrade carapace. Additionally, Scourge benefit from the carapace upgrade, allowing them to avoid dying from bounce damage while closing in. It should be mentioned that because damage is counted as either an integer or a half, the numbers won't work out exactly as mentioned above, but it was just to give an example.
Upgrades' effectiveness increases as your number of units increases, so if you are getting a carapace upgrade, you are better off trying to defend and accumulate Mutalisks rather than playing a skirmish style of play. Similarly, if you suspect your opponent is stalling for his carapace upgrade to finish, you want to engage in skirmishes with Scourge and Mutalisks. If you are playing a map conducive to fast expansions and macro, you should begin the carapace upgrade as soon as your Spire finishes. If you are playing a more aggressive map, I would avoid the upgrade until you have at least expanded.
It is worth mentioning that some players have said that the cost differential between the second carapace and first attack upgrade make it more reasonable to upgrade attack rather than carapace as your second upgrade. While this may be true, if you are playing a game that is going long enough for you to consider a second upgrade, your Mutalisk numbers should be large enough that one less Mutalisk while you research the second carapace upgrade should not matter. If you are trying to punish your opponent while you have a carapace upgrade and he doesn't (much like Protoss does to Zerg while +1 weapons is finished before carapace), do not research a second upgrade. Time your attack to be maximized as soon as the upgrade completes.
Both carapace and attack upgrades can be considered against Hydralisks. Generally, attack upgrades allow Mutalisks to deal additional damage to enemies, assisting in Hydralisk and Spore Colony sniping. Armour lets the Mutalisks soak up more damage and thus allows Zerglings to move in to the Hydralisks to attack. Both options should be considered, and, depending on the situation, one should be chosen over the other.
There are pros and cons to grouping with an Overlord. If you do group with an Overlord, your Mutalisks are easier to control when you are targeting and raiding, and they are much harder to Scourge. However, you are more likely to lose that Overlord in this match-up. Losing an Overlord is actually a fairly big deal in Zerg versus Zerg. Also, when you get in large Mutalisk battles, the ones that stay clumped together tend to lose to the ones that fan out around them. This is because the targets are much closer together, which allows for a definite bounce hit. What I personally do is group them with an Overlord at the start of the game, and as our groups become larger, I'll ungroup them.
You should always focus fire when getting in small Mutalisk battles (less than twenty). A dead Mutalisk doesn't do any damage to you; several hurt Mutalisks do. In this vein, your groups should contain at most seven Mutalisks, since 7 * 9 * 2 = 126, meaning you will kill a Mutalisk in two shots and not waste any damage. If either of you had upgraded, adjust accordingly. Once your numbers get larger than twenty, forget about this and just group everything together. Once the battle starts you should focus more on bringing in reinforcements and Scourging properly.
 Using Overlords to soak damage?
Overlords soak up Mutalisk bounce damage (they take damage that otherwise would have been dealt to a Mutalisk). Is this going to make up for the fact that he has 10 more Mutalisks than you? Of course not. Will it tip the balance in your favour with equal numbers of Mutalisks? Yes. It doesn't warrant getting the speed upgrade to use this tactic, but it is something to remember, especially in the case of close positions (Paranoid Android, Lost Temple, Python). Keep in mind that Overlords benefit from the Carapace upgrade as well, allowing them to soak up more bounce damage before dying. This is especially important in big, end-game Mutalisk battles.
 Using Mutalisks vs. Terran
Mutalisk Harass vs. Bionic Terran serves two main purposes: the Zerg will be able to slightly damage the Terran's economy, and the Zerg will have total map control, giving him time to expand (get a third gas) and tech to Hive units. Aggressive Mutalisk play such as 2-Hatch Muta requires that the Zerg do sufficient damage to the Terran to make up for being behind economically.
Eleven is the ideal number, with such, in two hits from every Mutalisk you can leave Missile Turrets with 2 remaining Hit Points, taking about two seconds more for the Turret to die. With five Mutas you can start killing marines in one hit, with seven, you can do the same to scvs. Ideally you never want to hit the same unit twice as they may move away, exposing your Mutalisks to enemy fire when they pursue.
You should always aim for having eleven Mutas at a time, until you're done harassing and different units have replaced their usefulness. You might think that if the Terran player built a dozen Turrets in response, your Mutalisks have already done more than enough; this is not always true however, because the economic strain in making those Turrets translates into fewer Marines and later tech which would otherwise negate your harass. By switching immediately after just having eight or nine Mutas, towards Lurkers, for example, you risk making his relatively small army, effective, because you have created a window where it's comparable in strength to your own.
When facing a bionic style of Terran, or one that uses Wraiths, upgrading Attack is better. You reduce the amount of hits required to kill a Marine from five to four; SCVs will die in six hits rather than seven and Missile Turrets die in twenty hits instead of twenty three, making them die instantly in two rounds of hits from eleven Mutalisks with no chance of repair from the Terran. Versus Wraiths, the Attack upgrade lowers the hits needed from fourteen to twelve, the lower cost compared to Carapace fits with the usually low-econ game Wraiths are involved and the Terran will usually follow a Wraith opening with Marines and Medics.
Against a mech-oriented style of Terran, upgrading Carapace is better as it completely negates the goliaths anti-air upgrade, effectively making your Mutalisks great damage sponges.
 Mutalisks versus Mechanized Terran
Against a Mechanized Terran, Mutalisks lose a lot of their effecitveness because of the range of Goliaths. However, the one advantage that Mutalisks have over Goliaths is mobility. If the Terran pushes out too early or takes an expansion too early, you can use Mutalisks to punish him. Goliaths will be forced to run all over the place to try and catch the Mutalisks. Since you should have at least a control group and a half of Mutalisks, you can use them to take out key tech buildings such as the Science Facility or Armory. If the Terran makes the mistake of moving his entire Goliath force to counter your Mutalisks, they can rejoin with your Hydralisks relatively quickly to take out any Siege Tanks that the Terran left out in the open.
 Using Mutalisks vs. Protoss
Your target against Protoss is undoubtedly the Probes. Cannons are not strong against groups of more than 8 Mutalisks, so don't fear unprotected Cannons. Once the Cannons are dead, target Probes while dodging Archons. Keep an eye out for fresh Templar warping in that can be easily picked off. Don't bother with high HP buildings like the Templar Archive. If you had enough time to kill a building like that, you've only let the player come back into the game, as he has undoubtedly added several Cannons to his supply lines now.
 Dealing with Archons
Over Battle.net, you generally shouldn't do it. But there are a few times when it's not a bad idea to go after an Archon. These situations break into two groups:
The first, is engaging an Archon. You would want to do this when the mineral line is well defended, but the main base isn't. If you can kill the roaming Archon, you have free access to kill Gateways and Tech buildings, as well as any new Templar that warp in. To do this, simply spread your Mutalisks as much as possible and engage. I always like to send one Mutalisk in first and run it past the Archon, thereby ensuring my grouped Mutalisks aren't taking splash damage until I have them spread. Obviously any decent player is going to target a clumped group of Mutalisks, so get them spread as soon as possible. If the Archon begins to run, give chase, while avoiding clumping back up again.
The second situation is sniping an Archon. This works similarly to fighting Marines - fly straight at it, fire and retreat before entering the Archons range. You can do this at any time, but it only makes sense to do it from above a cliff or when the Archon is having trouble getting through a Probe line.
The easiest way of destroying an Archon is creating a box of around 8 mutalisks. This box, is the exact opposite of a stack - it is supposed to surround the Archon in order to minimize the damage taken.
If you choose to avoid the Archon rather than engaging it, be sure to look for places, structures, and map features that will allow you to take advantage of your mobility. For example, on Neo Medusa, if you position your mutas on the high ground when harassing the probe line in the main, the Archon must first travel a long distance to engage your Mutas. However, when he does that, you can simply move your Mutas a few blocks over to the lower ground, where the Archon will be forced to work his way back down. By doing this, you are essentially making it impossible for the Archon to counter your Mutalisks without help from other units.
 Dealing with Corsairs
Fighting Corsairs is similar to fighting an Archon head on. Lead with a Mutalisk and run it past the group of Corsairs to allow your grouped Mutalisks to avoid taking splash damage. Spread your Mutalisks around the Corsairs and target them one by one. If you want to be cute, run damaged Mutalisks away and return them to the battle after another Mutalisks has been targeted by the Corsairs. If you are going to Scourge the Corsairs, make sure the Scourge are either spread out or cloned, and always attack from a different direction than the Corsairs are firing to avoid losing valuable Scourge to splash damage.
Always upgrade carapace against Corsairs.
 Sniping High Templar
In modern Zerg vs. Protoss, Mutalisks are used to snipe enemy High Templar. Without Psionic Storm, any Protoss army falls prey to a sufficient number of Hydralisks. The ideal number of Mutalisks to snipe High Templar with is 9. With 9 Mutalisks, 1 hit from each Mutalisk will kill one High Templar. 10 may be used if you are unsure of your Mutalisk Micro. However, you must be aware of the Protoss army composition. This technique of Templar Sniping works best when facing a Zealot/Templar/Archon army composition. In this case, the only real defense that the enemy has against Mutalisks are Psionic Storms since Archons have a very small range. Since the enemy has no Dragoons, the best way to snipe Templar is to keep your Mutalisks over the enemy's Zealots so he cannot storm unless he wants to hit his own army. Avoid any Archon fire and snipe as many Templar possible. In addition to killing High Templar, Mutalisks will be used as cost effective if you waste their energy Storming your Mutalisks because if the Protoss army does not have any Storms, fighting against Hydralisks will be suicide. Do not forget that your Mutalisks can also attack Zealots as well, but make High Templar your priority.
If you are fighting against a Dragoon/Templar army composition, then Mutalisks should not be used because you would lose too many Mutalisks to Dragoon fire.
 Further Resources
- GG.net thread about Mutalisk Micro - vs Scourge using patrol, Move-Shot, Chinese Triangle
- ZvsT Mutalisk micro UMS map - Lost Temple
- Mutalisk Micro UMS map - Python, by Grobyc. ZvT and ZvZ situations, three difficulty levels
- http://www.youtube.com/watch?v=NfqQYJzq7o0&feature=channel_page - An instructional video on air unit stacking and basic micro.
- ZvZ Mutalisk Micro Tutorial by ret.
This page is based on Chill's Mutalisk Guide from the Strategy forums, with some adaptations for a more wiki-esque style. Find the original here. Some information taken from this thread regarding stacking.