Metallica, the seventh-biggest recording act in American history, are consummate musicians, but it wasn’t always that way. Their early career is marked by a gradual evolution from garage-level thrash to sophisticated, progressive heights – an evolution driven by their bass player, Cliff Burton.

Burton pushed the band to new heights with his musical training, songwriting ability, and phenomenal bass skills across three albums: Kill ‘Em All (1983), Ride The Lightning (1985) and Metallica’s undisputed masterpiece, Master Of Puppets (1986). He was the first heavy metal bassist since Black Sabbath’s Geezer Butler to regard the bass as a lead instrument, delivering intricate live solos based on classical fugues and even laying down a solo track on Metallica’s debut album.

Cliff’s life was short but influential; his death was sudden and shocking. At the age of just 24, he was killed when Metallica’s tour bus overturned on a remote Swedish mountain road in the early hours of September 27 1986, crushed to death after being thrown from his bunk through a window.

With Cliff’s death, Metallica’s most critically acclaimed period of activity ended. They went on to record huge-selling albums, but by their own admission never pushed the creative envelope as radically as they had done in the first four years of their career. In 2006, a group of dedicated Metallica fans unveiled a memorial to Cliff at the site of his death; the cult of Burton grows year on year, with bassists of many musical styles (even outside heavy metal) acknowledging his influence.