|Area of Operations||Worldwide|
|Enemies With||No one specifically|
|Affiliated With||Regular Army, Rebel Army|
The first units in this group appeared during the "the King of Fighters 20th year celebration event". Characters were originally placed on either the Regular Army or the Rebel Army. Eventually, more were added over subsequent updates until enough existed to group them off into their own faction - eventually a KOF-themed zone was added to the world map (using music from their games). Repeated plays there eventually uncover an invitation leading to a hidden stage where Rugal (the sole boss-tier unit of the faction) can be unlocked for purchase.
While they were featured in KOF titles before any Metal Slug-related games, Leona, Ralf, and Clark remain as Regular Army units for the purposes of Metal Slug Defense / Metal Slug Attack. Unlike the other KOF team members (who use art unique to the mobile games), the Ikari Warriors' sprites are based on their appearances in Metal Slug 6 and Metal Slug 7/XX.
Whip and Heidern are the only KOF units so far who made their way into Metal Slug Attack. As no KOF faction currently exists in that game, they were currently assigned as part Regular Army with their fellow Ikari Warriors Team. They are also featured in both the Extra Ops and Another Story modes, complete with their own side stories. Two Slug Armors based on Kyo and Iori also appear for the "King of Weapons" event although placed in the Independent Faction.
During a crossover, Terry Bogard, Mai Shiranui, K', Kula Diamond and Athena Asamiya were introduced into Metal Slug Attack. As the KOF faction is still nonexistent in that game, they are all affiliated with the Regular Army, although Athena serves as a Supporter unit.
- All characters' animations are redrawn versions of their arcade counterparts, however, most of their defeat animations are variations of the standard Metal Slug death animation. The males use Marco's rolling death (except Kyo, Benimaru and Goro) while the females use Eri's toss death. Chang's defeat animation is based on the fat characters being popped inside out.
- Even though most of the KOF Team do not show up again in Metal Slug Attack, avatars sold in the Dress Up Shop do feature them including new sprites for characters in later KOF games. The 2019 KOF mobile game, KOF: Chronicle, uses a similar 2D, Tower-Defense gameplay of Metal Slug Defense and Metal Slug Attack with the same Metal Slug-inspired sprites.
|Regular Army||P.F. Squad • S.P.A.R.R.O.W.S • Ikari Warriors • Metal Device Project|
|Rebel Army||Rebel Infantry • Arabian Infantry • Future Rebels • ACE • Blaze Brigade • "Frozen Brigade"|
|Large Scale||Martians • Amadeus Syndicate • Ptolemaic Army • Invaders • Oguma Corporation|
|Small Scale||Japonese Army (Division 6) • Pirates • KOF Team • Mummy Army • Red Goblin Society • Secret Sect • Vampires • "World Military Corp." • Yuki Tsuki Hana|
|Mixed||Space Army • East • Another Force • Desert Army • Revolution Army|