Marco and Tarma are back to blast their way through another action-packed adventure, picking up various weapons along the way. The Slugs are also back and more colorful than ever, with Slugmariners, Drill Slugs and Elephant Slugs joining the original Metal Slugs and Slugnoids. As with previous titles, there are hidden items to be found and POWs to be rescued, while a branching map lets players take a different route to the end with each play-through.