Guitar Hero: Metallica

At the main menu, select "Options", "Cheats", "Enter New Cheat", then enter one
of the following codes to unlock the corresponding cheat option. If you entered
the code correctly, a message will appear.

Metallica Costumes
Press Green, Red, Yellow, Blue(2), Yellow, Red, Green.

Hyperguitar, Hyperbass, and Hyperdrums
Press Green, Blue, Red, Yellow(2), Red, Green(2).

Performance mode
Press Yellow(2), Blue, Red, Blue, Green.

Invisible Rocker
Press Green, Red, Yellow(3), Blue(2), Green.

Air instruments
Press Red(2), Blue, Yellow, Green(3), Yellow.

 