Metroid is a popular action-adventure video game series developed by Nintendo, first released in 1986. The series follows protagonist Samus Aran, a bounty hunter who combats the Space Pirates and their attempts to harness the parasitic Metroid creatures. Known for its non-linear gameplay and exploration, Metroid has been influential in the gaming industry, inspiring the 'Metroidvania' genre. The series is praised for its atmospheric storytelling, intricate level design, and pioneering of gameplay mechanics that emphasize exploration and discovery.