Metal Slug was conceived by the same staff who created several titles at Irem that shared similar presentation such as In the Hunt and GunForce II, with the core concept during development being a simple but exciting side-scrolling shooter featuring a very easy control scheme and visuals inspired by the works of Hayao Miyazaki. Set in 2028, players assume the role of Peregrine Falcon Strike Force soldiers Marco Rossi and Tarma Roving on a fight against the Rebel Army led by Donald Morden and overthrow his coup d'état to prevent a New World Order.

It is the first installment in the eponymous series. Metal Slug is a 1996 run and gun arcade video game originally developed by Nazca Corporation and released by SNK for the Neo Geo MVS.