Metal Slug 4 is a run and gun game for the Neo Geo console/arcade platform created by SNK. It was released for the Wii Virtual Console and the Nintendo Switch and is the fourth video game in the Metal Slug series.
Metal Slug 4 retains the same gameplay as previous titles, with the addition of some new enemies, bosses, weapons, vehicles and a new bonus combo system.
A bonus scoring system was added that allows the player to be rewarded depending on how many enemies are killed in the time allotted. The time allotted is determined from the type of emblem that is picked up. A time meter will appear on the top of the screen, and if the player lives through the end of the level, they will be awarded bonus points for badges that represent feats accomplished.
One year after the events of Metal Slug 3, the world is trembling under the new threat of a mysterious but deadly cyber virus that threatens to attack and destroy any nation's military computer system. With Tarma and Eri unable to help due to their own assignments in the matter, Marco and Fio are called in to investigate the situation and are joined by two newcomers, Nadia and Trevor. In their investigation, the group discovers that a terrorist organization known as Amadeus is behind the nefarious plot and that they head into battle against Amadeus' forces, hoping to destroy the cyber virus before it gets the chance to wipe out the entire world's military computer system.