Metallica formed in 1981 when drummer Lars Ulrich posted an advertisement in a local L.A. newspaper. Their early recordings featured fast thrash tempos, instrumentals, and a raw aggression that made them metal gods almost instantly. Here are the stories behind such songs as “Ride the Lightning,”  “The Thing that Should Not Be,” and “The God that Failed”—written about the death of lyricist James Hetfield’s mother.