The aspect of the Metal Slug series was to create a simple, but exciting side-scrolling shoot-em-up game with an easy control scheme (one joystick and three buttons). The same team that created Metal Slug for the Neo-Geo previously created several games for Irem which have very similar graphics and gameplays, such as GunForce (1991), In the Hunt (1993) and Gunforce 2 (1994).

Some of the stock sound effects and sprites from Irem and The King of Fighters titles were used in the Metal Slug games. The music was composed by Takushi Hiyamuta (who is credited as Hiya!), a key member of the Nazca Corporation, which was acquired by SNK in 1996. The first three titles were developed by the Nazca team before SNK declared bankruptcy in October 2001, leading to the disbandment of the original team. Anticipating the collapse of SNK, the company Playmore was launched in August 2001, which became known as SNK Playmore in 2003, the year after Metal Slug 4 was released. Development on the series has since continued without the original staff, with Noise Factory handling 4, 5, 6, and 7.