Alpha Metroids are larger and more aggressive than their larval counterparts. They fly faster and have a more robust defense. They still attempt to latch onto Samus, but their attacks are more damaging.
Strategy: Alpha Metroids are vulnerable to missiles. Aim for their underbelly or head. A charged shot from your Arm Cannon can also stun them, allowing for easier missile hits. Dodge their charges and be prepared to fire multiple missiles to take them down. The lava will recede further after each Alpha Metroid is defeated, revealing new paths.