Mega Man X is a robot designed by Dr. Light to choose his own path in life. Years after he is created, Dr. Cain finds X and mimics his design to create a race of such robots called reploids. When the sigma virus infects these reploids, causing them to commit acts of evil, it is up to Mega Man X and his partner Zero (who is quite powerful, contrary to what his name implies) to stop it.
The gameplay in Mega Man X involves navigating through various levels, fighting against hordes of reploids, and using the robot's abilities to overcome obstacles. Players can also collect power-ups and upgrades to improve their chances of success.