It began with rainfall and the toll of a mourning bell, before the unholy thunder of a three-note riff that would provide a catalyst for the next 40 years of heavy metal…

The song, the album and the band: Birmingham's finest, Black Sabbath.

Guitarist Tony Iommi's monolithic blues riffs are still the genre distilled in its purest, darkest form and Sabbath's first six albums remain an essential right of passage for any budding metaller.