Metal Doors are similar in appearance and accessibility to De-energized Doors, and appear in the 2D Metroid games. When Samus enters a room, the door behind her may lock and other times, she will find an area with several Metal Doors already in place. Usually they will only deactivate, allowing Samus to open them, after she has completed a task. The task usually involves purging the area of enemy hostiles, killing a boss, or returning power to machinery, however, some Metal Doors will never open and serve as one way passages through an area.
Super Metroid manualEdit
"Metal Doors can only be opened when they are flashing. You can make Metal Doors flash by defeating certain enemies."
Metroid Zero Mission manualEdit
"Meeting certain requirements is the only way to open these hatches."