Metal Slug- 1st Mission -normal Download | Link-

No legal free “normal download” exists directly from SNK for this title. If you own the original cartridge, you may legally dump your own ROM for use with an emulator. Tools like the Neo Geo Pocket Flash Linker or a Retrode can assist. Emulators: Mednafen , RACE (NGP) . 5. Conclusion While no legitimate direct “normal download link” is available for free, you can purchase the official SNK re-release on Switch/Steam. Avoid shady ROM sites; they offer no legal protection and risk your device’s security. If you need help finding the official store page for the game, let me know and I can point you there.