"Master of Puppets" is an tier 6 song featured in Guitar Hero: Metallica. It is a long song that includes strange time signatures interspersed within the song, as well as a oddly charted main riff. It also has faster parts then other parts of the song do. There are 2033 notes in "Master of Puppets" on Expert.
The ending note on Expert Guitar is a GRYB chord, one of the few songs in the franchise to utilize a 4-note chord. Due to the much needed strumming, very fast speed, very long time period and very hard solo, "Master of Puppets" might be considered very hard indeed, but still lacks that craziness that makes it as hard as "Dyers Eve" and "War Ensemble", arguably the two hardest songs in the game.
Everyone sings Master when it's sung.