The Mutons are a heavily modified race. They have cybernetic implants that enhance their cardiovascular system and their senses, giving them enhanced combat performance. For protection, an artificial skin has been grafted onto the body. The skin is very tough and armor piercing ammunition is not very effective against it. Their reproductive organs have been surgically removed.
The Muton soldiers are intelligent, but they do rely on telepathic commands from their masters. If the telepathic link is broken, they will break down and die.