Metallica frontman James Hetfield has admitted that the band's notoriously volatile relationship has helped keep them together.

Since forming in 1981, Metallica survived line up changes and fall-outs to sell 100million albums worldwide - which is a figure second only to the Beatles.

“Our relationship is part of what makes Metallica special. If everything goes smooth all the time then something is wrong,” Hetfield told the Sun newspaper.

“You have to have friction as it creates energy, brainstorms, pro-activity and we go forward.”

The band reached one of their lowest ebbs in 2003, when their last album 'St Anger' was poorly received by critics and fans.

While Hetfield conceded it was “was the low point of the roller-coaster” he added that the band were “back at the top now”.

Metallica release their long awaited follow-up, 'Death Magnetic', on September 12th.

(by Jason Gregory)