The biggest difference from the previous titles is the addition of the slide move, which allows the player to evade and maneuver in a new fashion. Unlike its predecessor, which reused many of the backgrounds from the previous games, Metal Slug 5 incorporates a wealth of new environments and backgrounds, and features a more Heavy Metal influenced soundtrack.
The laboratory developing the next generation of METAL SLUGs comes under attack and a data disk containing METAL SLUG secrets is seized.
Marco and Tarma are ordered to retrieve the disc and rush to track it down. Meanwhile, Eri and Fio, who are investigating the paramilitary organization Ptolemaic Army that is raiding historical ruins, succeed in tracking it down at an ancient ruin known as the "Corridor of Fire." They storm the site and attempt to overtake them, but they are repulsed by the natives and giant METAL SLUGs. This incident makes it clear that the enemy behind the pilfering of METAL SLUG secrets is the Ptolemaic Army.
The Government Forces decide to carry out a second assault on the "Corridor of Flame" using an elite force of PF Squad and S.P.A.R.R.O.W.S. members to retrieve the secrets and destroy the paramilitary organization!!
A special disc that contains deep and intricate secrets about the Metal Slug project is stolen by a mysterious group called the Ptolemaic Army, whose specialty lies from within archaeological excavation and espionage. Marco and Tarma of the Peregrine Falcon Strike Force follow in hot pursuit against the group and in the process are joined by Eri and Fio of SPARROWS. Together once more, the quartet investigate the shrouded objective of the Ptolemaic Army.