Check out these great songs and albums to get a basic understanding of what was happening in 1970 and why this year is regarded as the birth of heavy metal.
The songs and albums are focused solely around "the unholy trinity" of Black Sabbath, Deep Purple and Led Zeppelin. It is widely recognized that these three British bands were the most influental ones in the very early stage of the genre.
Songs
Black Sabbath: "Black Sabbath" (from the album Black Sabbath)
Black Sabbath: "War Pigs"
Black Sabbath: "Paranoid"
Black Sabbath: "Iron Man" (all from Paranoid)
Deep Purple: "Speed King" (from Deep Purple In Rock)
Deep Purple: "Black Night" (non album single)
Led Zeppelin: "Immigrant Song" (from Led Zeppelin III)
Albums
Black Sabbath: Black Sabbath
Black Sabbath: Paranoid
Deep Purple: Deep Purple In Rock
Led Zeppelin: III
It is also widely recognized that Black Sabbath was THE most important band out of the three. The title song from their debut album is a groundbreaking moment, with its sinister distorted tritone guitar riff, rich bass, thunderous drumming and dramatic vocals. Sabbath followed up their early metal sound the same year with their most succesful album Paranoid - featuring three of their signature songs. The line-up of Ozzy Osbourne (vocals), Tony Iommi (guitar), Geezer Butler (bass) and Bill Ward (drums) also remained consistent all through the 70's and though they evolved their music was always rooted in the metal sound they created in 1970.
Deep Purple also made a huge impact as they renewed their sound in 1970 with a new singer in Ian Gillan, bass player in Roger Glover the now combined distorted forces of exisiting members Ritche Blackmore's guitar and Jon Lord's hammond organ.
It remains controversial how important the mighty Led Zeppelin's role was in the history of heavy metal. Actually, their two albums from 1969 were more hard rock based than their third but the opener "Immgrant Song" certainly fits the hard rock narrative of 1970 perfectly.