Mutons, like the other original aliens, have been altered with human DNA. They look little different to their predecessors, but are otherwise very similar. They're quite durable, with 8-11 health and 1-2 armor, depending on difficulty. They are armed with three weapons: Plasma Rifles, which deal 4-6 damage and shreds 1 armor; a bayonet attachment, dealing 6-8 damage; and Plasma Grenades, dealing 4-5 damage and shredding 2 armor.
The Muton AI likes to close in and use the bayonet. Attacking them in melee is ill advised due to their Counterattack passive ability, which automatically nullifies a melee attack and immediately responds with one of their own. Their Bayonet also has a chance to stun, complementing the Execute ability.
Mutons can Execute an adjacent stunned enemy, killing them regardless of remaining HP. A stunning Counterattack followed by an Execution can and has cost the life of many favoured and overzealous Rangers.
Seeing multiple soldiers close together may make them use their grenade. They can also use the classic Suppression ability, which pins down the target, lowering their Aim and forbidding movement on pain of an Overwatch shot.
Counterattack is nullified with Disorientation, making them safe to cut apart. Their Will is also poor, making them vulnerable to Psi Operative abilities.