Metallica is a heavy metal band that were hugely popular in the 80s and 90s. They lost a Grammy the first year the Grammy's introduced the Heavy Metal award to Jethro Tull. Metallica has some iconic songs like Enter Sandman, The Unforgiven, and Nothing Else Matters.
Lars Ulrich whining about Napster made a lot of fans that liked them turn on them because they were against the few distribution of music. The RIAA has used the Napster case as a money grabbing front since then.