Some APKs bundle a Neo Geo emulator (e.g., MAME4droid, Neo.emu) with ROMs. These:

Each entry in the series maintains the core loop of saving POWs and destroying massive mechanical bosses while introducing unique mechanics:

Getting Metal Slug 1, 2, 3, 4, 5, and 6 all in one APK sounds like a dream for run-’n’-gun fans — and when it works, it’s pure nostalgia overload. The pixel art, over-the-top weapons, and hilarious enemy animations hold up perfectly. Metal Slug 3 alone is worth the download, with its branching paths and insane final mission.