Judas Priest, the second indisputably metal band burst onto the scene in 1974... although it was with little fanfare.

While Black Sabbath took a short break from recording amid turmoil between band members, their fellow Birmingham natives stepped up to the plate with their first full-length, Rocka Rolla. Judas Priest had finally managed to put a together a stable lineup in 1973 with the addition of Rob Halford on vocals and Glenn Tipton on guitar. Along with guitarist K.K. Downing, bassist Ian Hill and drummer John Hinch, the band entered the studio

Entering 1973, Black Sabbath found for the first time that they were creatively spent.

The band was still touring as hard as ever. They were even playing successful shows as far as Australia and New Zealand. When the fearsome foursome finally got down to writing a new album, however, they discovered that they had completely run out of ideas.

Black Sabbath's seemingly unstoppable momentum almost came to a crashing halt in 1972.

Musically, the band was continually reaching new creative peaks. They released their fourth album, aptly titled Volume 4, on September 25. The LP featured some big steps forward for the band, most notably the prominent use of keyboards and synthesizers.

How do you follow the unfollowable?

Black Sabbath one-upped themselves in 1971 with Master of Reality, an album that was arguably even more impressive than its predecessors - 1970's Black Sabbath and Paranoid. The new LP contained many of Sabbath's most creative and groundbreaking songs.

Black Sabbath invented heavy metal in 1970. Period.

Many rock historians will point to late '60s/early '70s hard-rock and heavy-blues bands like Led Zeppelin, Deep Purple, Iron Butterfly and even Cream as having created heavy metal. The truth is that they merely helped lay the groundwork. They were not heavy-metal bands. Black Sabbath were a heavy-metal band.