Alpha Metroids
The first stage of the Metroid evolution cycle, they will fly around and attempt to ram the player. They are impervious during ramming, but are easy to take down outside of it.
Gamma Metroid
Gammas will crawl around, sometimes clinging to walls, before attempting to leap on the fighter. If successful, it will cause an effect similar to the Bucculus in Brawl, in which it will deal damage for a bit before jumping off. The speed of when they jump off can be sped up by button mashing while it's on the player. Once the initial attack has subsided, they will act as a normal enemy, and will shoot electric beams at the player from their mouths. If they crawl on a wall again, they will repeat the initial attack.
Zeta Metroid
Zeta Metroids act as mid bosses of sorts, being extremely strong. If the player is close to them, they will swipe at them, but if the player is far away, the Zeta will either pursue them to get the player in range of it's attacks, or if the player is in range, attack them. Zetas can shoot acid, which creates a poison floor effect wherever it lands for a short while. The acid itself doesn't deal much damage. They can also shoot long streams of fire, which deals moderate to high damage depending on how many hits connect. It can also jump onto the ceilings and walls to perform these attacks. Zetas have a weak point in their underbelly, and attacks will deal more damage there.
FG-ll Ghrahams
FG-ll Grahams will fly around the map. Upon seeing the player, they will charge missile shots to hit them, or attempt to ram them. They can only be harmed while charging their shots. They have low health however.
Pirate Trooper
Pirate Troopers take their appearance from Metroid Prime 2: Echoes. They can attack by either slashing at the player or shooting at them with their weapon. They are easy to take down however.
Shriekbat
Shriekbats live on ceilings in groups. Upon the player getting in range of them, they will jump down and attempt to dive bomb the player. The player can defeat them midair or take them from a distance with ease, as only one or two hits knock them down. However, the number of Shriekbats may make it difficult to strike them all. They deal mediocre damage upon a successful dive bomb, at which point they will explode with it.
Desgeega
Last one, Desgeegas. These will hop down from ceilings and attempt to stomp the player. Their legs are good shields, allowing them to take hits much better when hit from the side. If hit from the top however, they will take increased damage. They will attempt to jump on the player as their attack.