The idea of watching a heavy metal rock band in therapy for entertainment may seem absurd. But that's the premise of Metallica: Some Kind of Monster, a documentary filmed as Metallica were recording their award-winning album St Anger. Released in the US in 2004, the film went by unnoticed in Hong Kong, except for a few diehard heavy metal fans. But it is worth watching because rock 'n' roll is perfect material for films. You can never fully appreciate the music of a band without seeing how these self-indulgent and self-loathing gods of rock - with too much money, talent and hardship - make a mess of their lives before trying to pull themselves together through music. The story begins at the band's lowest point. Bassist Jason Newsted has just left the band, and the group haven't worked together for a long time. What's more, they are no longer angst-ridden, foul-mouthed rockers but family men whose children visit them at work. But how can you play heavy metal rock music with a child on your lap? No wonder the group needed a therapist. Their shrink is paid US$40,000 a month to keep everyone in the band happy. He is experienced in nursing the bruised egos of sports stars. At times he sounds like a marriage counsellor to the band, which is on the brink of falling apart. The documentary is honest, so honest that it even shows James Hetfield, the band's frontman, complaining about being the subject of the film. It also unveils the subtle power play between Hetfield, whose passive-aggressive tactics contrast sharply with his fearsome beer-drinking image, and drummer Lars Ulrich, who appears to be the frustrated victim but is in fact as much a self-absorbed control freak as his musical partner. Few documentaries are capable of capturing the kind of artistic and personal tensions that have torn so many great bands and friendships apart. The success of Metallica: Some Kind of Monster lies in the way it reveals the monsters in everyone, whether it is alcohol, drugs or self-pity. The mood is melancholic rather than triumphant when the band finally completes the album. The flashbacks of 'the good old days', when the long-haired members of Metallica made sure everyone had a good time, remind us how strained the relationship between Hetfield and Ulrich has become. Sometimes when things get so bad, there is no reason to call a therapist. You just need to call it a day.