Joe Perry may have had a hand in shaping metal in Aerosmith's material, but he knew enough to know when what true metal wasn't.

Black Sabbath may have had their own niche in the rock world in the 1970s, but they knew there was a chance they could be thrown away at any time.

Despite achieving great commercial success, Ozzy Osbourne's favourite song didn't earn its creators celebrity status - making it a lesser-known gem.