Lemmy (real name is Ian Fraser Kilmister) is an iconic musician. He is the frontman of the popular band Motörhead. Motorhead's hit, "Ace Of Spades" has been featured in many music games. Because of this success, it's no surprise that Lemmy would end up being a character in Guitar Hero: Metallica, where he becomes an ulockable character after beating "Ace Of Spades".
Lemmy Kilmeister is also the voice of Kill Master in Brütal Legend.