This series, the Fatal Fury series, the Art of Fighting series and the Samurai Shodown series are the only SNK non-crossover series to receive characters from other franchises, whether from the company itself or from other companies.

Starting from Metal Slug 5, all the games were produced and released by SNK PLAYMORE. The four first games of the series were produced and released by former SNK, and Metal Slug 4, by PLAYMORE and BrezzaSoft.Participation of the characters in the mainline games of the series, either they canonical or not. Metal Slug Survivors / Metal Slug 4 Mobile.This leads to the ability for the player to run in and use melee attacks to take down a number of troops. In this series, contact only results in either party's death if an attack is performed. In most run and guns, contact with an enemy leads to immediate death. First and foremost is the ability to perform melee attacks.

Metal Slug however takes the concepts introduced in Contra and expands upon them. All of these characteristics come from the Contra series, which the game's mechanics is based on. The mechanics of the series is characteristic of run and guns: The enemies come in hordes, the weapons have high fire rates. Metal Slug 6 returned to the plot of the first three installments, bringing back Morden's Rebel Army and the Mars People. The fifth moved to the motif of modern guerrilla warfare, leaving only traces of the series signature quirky humor and paranormal enemies (except for the final boss). Outlandish elements were removed from the fourth game to return to the feel of the original title, which resulted in poor critical and commercial reception. In the games following the first, the PF Squad also battles an alien threat to Earth (the Mars People), as well as several other supernatural threats including yetis, zombies, ambulatory Venus flytraps, giant crabs and mummies. Later games featured characters from the Sparrows Unit, which is under the control of the Regular Army's intelligence division. The first game's story involved the Peregrine Falcon (PF) Squad, a small but skilled team of soldiers serving under the Regular Army's special operations division, who fight against the army of General Donald Morden in order to prevent a massive coup d'etat and the creation of a New World Order under General Morden. Special Illustration by TONKO for the SNK Brand 40th Anniversary.

Metal slug 1 was on which console