Metroid is the first in a long-running game series by Nintendo. It follows bounty hunter Samus Aran as she attempts to retrieve the parasitic Metroids that were stolen by Space Pirates, who plan to use the Metroids as biological weapons to destroy Samus and all who oppose them.
It was a unique game with a focus on exploration, nonlinear gameplay, and power-ups that could be used to unlock previously inaccessible areas. The game proved highly influential in its time and it, along with its sequels, continues to shape the design of indie adventure games to this day.
It was also one of the first games to feature a female protagonist, a fact which was revealed to the player upon successful completion of Metroid within five hours. Needless to say, the TASes published on this site complete the game in far less time.