In the early seventies, when Led Zeppelin and Black Sabbath ruled the world, Steve "Lips" Kudlow and Robb Reiner, two young Jewish boys from the northern suburbs of Toronto, vowed to rock together forever. A decade later, their band Anvil released one of the heaviest records in music history, Metal on Metal, which influenced a whole musical generation, including the world-dominating bands Metallica, Slayer, and Anthrax. Yet while these bands went on to sell millions of records, Anvil slipped straight into obscurity.

Was it too much sex and drugs and not enough rock 'n' roll? Was it the...