Metroid Database.com

The time it takes you to complete Metroid determines the ending you'll get. There are five (5) endings in the original Metroid. All of them begin with the screen shown to the left. From there, Samus begins flashing rapidly, and one of five transformations occurs:

ENDING ONE | Image

(< 3 hours)
Samus' armor disappears, revealing the hunter to be a woman. She's wearing a purple leotard and has brown hair. Pressing Start at the end of the credits allows you to start a new game as Armorless Samus.

ENDING TWO | Image

(3-5 hours)
Samus' helmet disappears, still revealing her secret identity by showing her with long brown hair, though still wearing her armor.

ENDING THREE | Image

(> 5 hours)
Samus raises her fist in victory, but the armor stays put.

ENDING FOUR | Image

(> 5 hours with Armorless Samus)
Samus flashes, and turns her back toward you and her arm thrown over her face in shame.

ENDING FIVE | Image

(< 1 hour)
After the flashing, Samus is wearing only a purple bikini. Getting through the game in under an hour is tough, but it can be done.