Countdown

Countdowns have long been the signature of the Metroid series. Often, after defeating the final boss, Samus must evacuate the location in a certain time. 6 minutes is a very frequent time limit, although 3 minutes and 1 minute have been known to appear as well.

Super Metroid
In Super Metroid, Samus must evacuate the Space Colony after defeating/damaging Ridley.

Metroid Fusion
There are many countdowns in Metroid Fusion. The first countdown happens in Sector 3, where Samus must race to the Main Boiler Room to stop the BSL Space Station from overheating and exploding in 6 minutes. Later, Samus must Space Jump to the top of a shaft with Metroids and the SA-X in 1 minute. In the final sequence, Samus has 3 minutes to escape the Space Station whilst it hurls toward SR-388.

Metroid: Zero Mission
In Metroid: Zero Mission, after defeating Mother Brain, Samus must escape from Tourian in 2 minutes by jumping onto various crumbling platforms.

Metroid Prime 2: Echoes
At the final sequence of Metroid Prime 2: Echoes, Samus must defeat Dark Samus and return to Aether whilst Dark Aether crumbles from loss of energy.