Heavy metal music
Critics disagree over who can be thought of as the first heavy metal band. Most credit either Led Zeppelin or Black Sabbath, with American commentators tending to favour Led Zeppelin and British commentators tending to favour Black Sabbath, though many give equal credit to both. A few commentators—mainly American—argue for other groups including Iron Butterfly, Steppenwolf or Blue Cheer. Deep Purple, the third band in what is sometimes considered the "unholy trinity" of heavy metal (Black Sabbath, Led Zeppelin, and Deep Purple), despite being slightly older than Black Sabbath and Led Zeppelin, fluctuated between many rock styles until late 1969 when they took a heavy metal direction.
Tony Iommi
Furthermore, Iommi is recognised by many as the main creator of heavy metal music. Brian May of Queen considers him "the true father of heavy metal", Eddie Van Halen states that "without Tony, heavy metal wouldn't exist. He is the creator of heavy!" and James Hetfield of Metallica, who was profoundly influenced by Iommi, defines him "The king of the heavy riff". Rob Halford, vocalist for Judas Priest, when filling in for Ozzy Osbourne during an August 2004 concert in Philadelphia, introduced Iommi to the audience as "The man who invented the heavy metal riff". Michael Amott of Carcass and Arch Enemy considers Iommi his "guitar hero" and the world's greatest guitarist "because he invented the heavy tone and evil riff". According to Lamb of God singer Randy Blythe, "Iommi is the reason heavy metal exists".