A paramilitary syndicate known as the "Ptolemaic Army" attacks a research installation that was developing the next-gen of Metal Slugs and with this, they have successfully stolen a disc containing Metal Slug top-secret data. Fearing that such information be used for their evil purposes, the soldiers Marco, Tarma, Eri and Fio received orders to recover the disk and put a end in this syndicate.The latest installment of the most famous arcade-shooting series brings a lot of changes: this time, you will not face Morden's army like in the previous games, but with a new group of enemies that composes the already mentioned Ptolemaic Army.To add more content to this title, 3 guns (Big Rocket, Big Laser and Big Shotgun) and 2 vehicles (Slug Sub and Slug Plane) from past games were reincorporated, as well as all brand new stuff of 3 vehicles (Spider Slug, Slug Gunner and Slug Car).The most important addition is a sliding move: pressing the B Button when ducking will make your character slide for a short time in the ground, which can be helpful to avoid some enemy attacks. During the sliding, you not be able to throw grenades, but your gun can be fired normally.