"Don't give up the day job." If ever there was a piece of 'advice' to strike terror into the hearts of those who have dreamed of doing something else with their lives it's this one.

But there are also those who just won't take 'no' for an answer, and as you scratch your head at them (head)banging theirs against a brick wall, you're filled with admiration and goodwill. Even if you hate heavy metal, you'll end up with a huge soft spot for Anvil.

Formed by school friends Kevin 'Lips' Kudlow and Robb Reiner in the late 1970s, Anvil were on the verge of the big time in the early 1980s but have spent the last twentysomething years in obscurity - their name known by millions of metal fans but that recognition not translating into album sales. Now in their early fifties, married and holding down jobs in catering and construction, Lips and Robb still dream the dream - but they both know that youth isn't on their side.

Music snobs whose reinvention of their own past involves listening to 'Blonde on Blonde', 'Kind of Blue' and the B-side of 'Low' at the age of 12 will approach 'Anvil...' with a smugness and superiority that suggests they'll learn nothing from watching. Others will get a lot more out of it. While there are funny moments, this is touching rather than laugh-out-loud and says more about male friendship and identity than many will give it credit for.

You'd need a heart the colour of tar not to cheer Lips and Robb as they lurch from one crisis to another, coming up against apathy, management disasters, domestic pressures, financial worries and the tensions in their own friendship. Throughout, Lips comes across as the guy with no intention of growing up, while Robb, the more introspective of the two, seems to have a firmer grounding in reality. But both of them have more heart and belief than know-it-all musicians half their age. Youth aside, what the younger ones have over the duo is the conviction that you don't have to rely on major label deals and 1980s business models to get your music out there - one of Anvil's biggest failings was that they hadn't moved with the times technologically.

Gervasi, an Anvil fan going back to his teenage years and a former roadie for them, skilfully weaves the highs and lows with insights from Lips and Robb's families. The duo may have regarded themselves as yesterday's men in their moments of self-doubt, but when you look at the love others have for them and the lives they've built, they're kings.

This story of a band stuck in the small-time but convinced that they deserve the big time is constantly fascinating, frequently poignant and sometimes excruciating. The 80 minutes go past quicker than one of Lips' solos and Gervasi's only failings are that his film should have been longer and included more interviews with the other two guys in the band, the former members and their views on Lips and Robb.

But that's a small complaint. Gervasi has a great future ahead of him and after the success of this film, so, it seems, do Lips and Robb.

Harry Guerin