The following are known Action Replay Codes for Metal Slug Advance on Nintendo Game Boy Advance (GBA).
These codes were also known as GameShark Codes and in most cases will work on both devices.

These codes are for the U.S. version of the game.

Master Code – Must Be On
2286524f
8e51fd40
3112d648
b66140ba

Infinite Health
da2f5ad7
2313c12e

Invincibility
6c869fe3
3316a68f

Infinite Bombs
961bc0cf
057174dd

Super Jump
2ff96ea5
d5206750
a0d99078
6883b588