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.
Christian metal
The first Christian hard rock group was possibly the California-based band Agape, formed in the late 1960s. Known for their psychedelic rock and blues influences, the band released an album titled "Gospel Hard Rock" in 1971, followed by "Victims of Tradition" in 1972. After Agape, the Resurrection Band was formed in 1972 in Milwaukee's Jesus People community and released the hard rock album "Music to Raise the Dead" in 1974. The Swedish group Jerusalem was formed in 1975 and is cited as another early Christian hard rock group. In 1978, Resurrection Band released its album "Awaiting Your Reply" and Jerusalem released "Jerusalem (Volume 1)". Both albums had a notable impact on Christian music culture. During that time, heavy metal was a new style of music for the Christian music industry, and many Christian labels did not expect it to sell well. However, "Awaiting Your Reply" hit big in the Christian market, and reached No. 6 on the Gospel album sales charts. "Jerusalem" also became an instant hit among listeners, and within the first six months the record sold 20,000 copies, unheard of within the genre of Christian rock in Europe. The Canadian Daniel Band is cited among the first bands, as is Barnabas.