Eastern Side of Area 3

Walkthrough: Past most of the Main Elevators of Area 3 is another large area. Go there after returning through the East Elevator, and then Save at the Station just above the Elevator. Go to the right after you do this, and jump down down into another long tunnel. At the end of this path, you'll find the Teleportation Statue. Enter the door just to the right, and use the Aeion Recharge. Jump up and use the Grapple Beam to swing across the area. Pull at the red glowing orb and then smash it. Swing across the next area, and then jump into the small hallway and shoot your Grapple Beam once more to grab the next red block.

Head upward, and then enter the door to the right. There will be three open rooms you'll find by heading in this direction, which is where you'll eventually find a Gamma Metroid by destroying the weak spot in the bottom right corner. The Metroid, like before, will move from room to room as you cause more and more damage to it. You have to continue to follow it as it moves, as you must defeat it in order to proceed further. After you defeat your fourth Metroid of Area 3, head back to the Teleportation Statue.

Missile Expansion: As you're falling downward in the very long tunnel apart of this section of Area 3, keep a lookout for another section where the wall and floor actually make a corner. Bomb that very corner to find the Missile Expansion.