The following are known Action Replay Codes for Metroid Fusion 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
e3867a25
806c0ddb
ae6b830a
a8006ef1

Infinite Health
c746328a
2787b50a

Max Health
8d44d82f
1c20c6f2

Infinite Missiles
a6f25692
a02899d7

Max missiles
91be71a8
e7cce188

Infinite P Bombs
75e86f4b
8a26f96a

Max P Bombs
60256c87
92373668