A horizontal-scrolling, parodistic World War II themed jump-and-shoot game. Extra weapons can be picked up and used for greater firepower, and vehicles (such as the "Super Vehicle-001"or Metal Slugof the game's title) can be entered and driven. The levels are also littered with bearded hostages who, when rescued, award the player with point bonuses (in the form of medals) and weapon power-ups. Metal Slug is a superb game which achieved the status of instant classic and is still considered by many to be the pinnacle of 2-Dimensional game design.
Meeher, the lead designer of the game for Nazca, wanted to create an armored fighting vehicle that could crawl on the ground like a 'slug', similar to a snail but without an outer shell protecting its body. The word "metal" in the title indicates that the vehicle is mechanical. Initially players regarded the title as being "not good enough". Meeher later joked about the title, saying "Maybe I don't make much of a sense?". Slugs in Metal Slug sequels included animals (usually only the Vulcan cannon mounted on the animal, with a cannon attachment occasionally available), planes and other vehicles that do not fit Meeher's original definition.
While being an obvious parody of World War II and the Nazi regime (the rebel army's flag is a deliberate pastiche of the Nazi Swastika), Metal Slug also lampoons Full Metal Jacket and MASH. General Morden, the rebel army's evil general, is a parody of Saddam Hussein.
Just as the 2 main heroes (Marco and Tarma) appear on every chapter in the Metal Slug series, General Morden and Allen O' Neill (the machine gun wielding, trash mouth-talking, buffed soldier) are the series' classic main villains.
The same team that created Metal Slug previously created a handful of games for Irem which have very similar graphics and gameplay. Cyber Lip (1990) had some of the same core developers as the original Metal Slug. Gunforce (1991) and In the Hunt (1993) had noticeably similar gameplay, with graphics that have a slight resemblance to Metal Slug. Gunforce 2 (1994) not only had similar gameplay but the sounds of dying soldiers were almost exactly the same as Metal Slug. Because of this, some fans refer to Gunforce 2 as "Metal Slug Zero". (arcade-history)