Metal Slug 3 is a run and gun video game for the Neo-Geo console/arcade platform created by SNK that was released in 2000 and is the sequel to Metal Slug 2. Being the last Metal Slug that SNK was working on until the bankruptcy, it was given a lot of features, enhancements and improvements. The music of the game was developed by Noise Factory. The game was later ported to the Wii Virtual Console and Nintendo Switch. The game was also released for the Wii as part of the Metal Slug Anthology.
The gameplay mechanics are the same as previous Metal Slug games. New for Metal Slug 3, however, is the branching path system; in most missions, there are forking paths for the player to choose from, each with their own obstacles, and of varying length and difficulty. All paths eventually lead to the same boss battle, but the player may have different equipment, and may have rescued more or fewer hostages depending on their choices.
The rebellion orchestrated by General Donald Morden to bring about a new global regime is now ancient history, and order and peace has begun to return to the world. Morden, brought back into power, was attempting another coup d'état, but government forces got wind of the plot beforehand and pre-empted the impending assault.
Instrumental in squashing Morden's Rebellion forces, Marco and Tarma of the Peregrine Falcon Strike Force are ordered to lead the team after their earlier requests for resignation were denied. Although General Morden has been written off as "missing" by his followers, they have hidden themselves throughout the world, and Marco and Tarma's abilities and experience are seen as a necessity to destroy remaining rebel strongholds, one by one. Throughout the furious fighting against the holdouts, Marco and Tarma cannot help but suspect Morden's involvement in this new evil plan for world domination.
Meanwhile, the SPARROWS, a special strike force within the government intelligence agency, have come across a series of strange events running parallel to the Peregrine's pursuit of General Morden. From trivial abductions of livestock to the disappearance of government officials and the appearance of freakishly large creatures, numerous occurrences with nothing in common point to one grim possibility. General Morden is not the only menace to worry about. Eventually it is learned that the alien menace that appeared in Metal Slug 2/Metal Slug X have returned. Once again, an ad-hoc alliance is formed to combat the external threat.