Activate the following cheats by entering the corresponding sequences of buttons at "Options" > "Cheats" > "Enter New Cheat".

R=Red, B=Blue, Y=Yellow, G=Green

CHEAT FUNCTION - CHEAT CODE
Air Instruments - RRBYGGGY
Always Drum Fill - RRRBBGGY
Always Slide - GGRRYRYB
Auto Kick - YGRBBBBR
Black Highway - YRGRGRRB
Extra Line 6 Tones - GRYBRYBG
Flame Color - GRGBRRYB
Gem Color - BRRGRGRY
Hyperspeed Mode - GBRYYRGG
Invisible Characters - GRYYYBBG
Metallica Costumes - GRYBBYRG
Performance Mode - YYBRBGRR
Star Color - RRYRBRRB
Vocal Fireball - RGGYBGYG

Unlock the following characters by performing the corresponding tasks:

CHARACTER - HOW TO UNLOCK
James Hetfield - Earn 100 stars in vocalist career.
James Hetfield Classic - Earn 150 stars in vocalist career.
James Hetfield Zombie - Earn 200 stars in vocalist career.
King Diamond - Beat the song "Evil" in any instrument career.
Kirk Hammett - Earn 100 stars in guitar career.
Kirk Hammett Classic - Earn 150 stars in guitar career.
Kirk Hammett Zombie - Earn 200 stars in guitar career.
Lars Ulrich - Earn 100 stars in drum career.
Lars Ulrich Classic - Earn 150 stars in drum career.
Lars Ulrich Zombie - Earn 200 stars in drum career.
Lemmy - Beat the song "Ace of Spades" in any instrument career mode.
Robert Trujillo - Earn 100 stars in bass career.
Robert Trujillo Classic - Earn 150 stars in bass career.
Robert Trujillo Zombie - Earn 200 stars in bass career.

Complete "The Thing That Should Not Be" in career mode to unlock "Broken, Beat & Scarred", "Cyanide", "My Apocalypse".

Unlock the following bass guitars by performing the corresponding tasks:

BASS GUITAR - HOW TO UNLOCK
Klown bass - Get 45 stars on bass.
Mean Green bass - Get 25 stars on bass.