Alpha Metroid:

Alpha - Are Mutated from Baby Metroid
Gamma Metroid:

Gamma - Are mutated from alpha, have attack "electricity"
Autoad:

Autoad - Are jump (how bunny)
Zeta:

Zeta - Mutated from Gamma. Attack with Hands
Omega:

Omega - Mutated from Zeta. +2 Damage to player (better than zeta)
Queen:

Queen - Are final or king of metroids. (Mutated from Omega)
Prime (Custom Mutation from Queen):

Prime - Mutated from Queen, +10 damage to player (better queen)