A gravel-voiced man sings Coldplay’s Fix You as if his heart will burst. A drummer plays Wild Thing as if he wants to smash his kit. Young men writhe in ecstasy as a band belts out Metallica tracks. It’s a scene played out a million times in the rock era – except that the gravel voice belongs to an 80-year-old, the drummer has Down’s syndrome and the metalheads are in Baghdad, where Iraqis have been shot for speaking English. They appear in three remarkable films which have their UK premieres at the Britdoc festival next week.

Jerry Rothwell’s Heavy Load follows three men and two of their helpers who have formed Britain’s first severe learning difficulties punk band. With the rhythm driven by the drummer, Michael White, they first startle, then captivate their audiences, making everyone from the Beatles to Kylie sound like the Sex Pistols on coke.

Then, in Stephen Walker’s Young@ Heart, a Massachusetts choir performs classic tracks by James Brown, Bob Dylan and Coldplay, despite having an average age of 80. Two of the choir actually died during the filming.

The most exotic and unexpected example of rock as existential defiance, though, comes in Heavy Metal in Baghdad in which the Canadian film-makers Eddy Moretti and Suroosh Alvi follow the struggle of five young Iraqis to emulate Metallica, Slayer and Slipknot despite curfews, power cuts, death threats and their practice room being pulverised by a rocket. We clearly need a new festival: Rock Against Stereotypi-cal Expectations, perhaps, or just Rock Against the Odds.

Heavy Load – the band – got going more than nine years ago and, according to Rothwell, “they have all the problems you would get with any band”. The project nearly collapsed, for example, when White threatened to leave. “It’s absolutely classic,” laughs the band’s bass guitarist, Paul Richards. “The drummer wanting to be the lead singer and then start a solo career.”

Meanwhile, the lead singer, Simon Barker, seems to have been in it for the groupie action. “He has real charisma,” Richards says. “He had a string of girlfriends while we were filming.”

Under the compassionate but strict musical direction of Bob Cilman, the Young@Heart choir achieves a remarkably high standard. “But the most extraordinary thing about it,” Stephen Walker says, “is that the most familiar songs take on a completely new meaning when they are sung by 80-year-olds.”

Nowhere is this better illustrated than in a scene where the octogenarians sing a haunting version of Dylan’s Forever Youngin the local jail. “I actually prefer their version to Dylan’s,” says Walker. “I turned the camera on the audience and it was extraordinary to see these hardened cons reduced to tears.”

Heavy Metal in Baghdad is the only film with a downbeat ending. It opens with archive footage of Acrassicauda (the Latin term for a black desert scorpion) performing in the Saddam era, when the band was forced to include a pro-regime track in each gig. A local reporter filmed them playing in an hotel after the invasion in 2003, their audience of young Iraqis in Megadeath T-shirts writhing in a mini mosh-pit. But when Moretti and Alvi catch up with them it has become too dangerous for Firaz, Tony, Faisal and Marwan (who speak flawless MTV American) to continue. By the end they have become penniless refugees in Syria.

“But making this film restored my faith in popular culture,” Moretti says. He is proud of the depiction of Iraqis as normal human beings, and what it shows about the appalling effects of the invasion on their daily lives.

All three films have sparked enthusiastic reactions. Heavy Load played New York last month. After screenings of Young@Heart one TV company even ran a bus-pass version of Pop Idol. Meanwhile Acrassicauda have reached Istanbul and are becoming a focus for pioneers of cultural freedom in the Middle East. To paraphrase Noël Coward, how potent popular music is, even in the strangest of circumstances.

Britdoc festival, Keble College Oxford, July 23-25. www.britdoc.org. Young@Heart will be shown on July 23 (4pm); Heavy Metal . . . on July 24 (8pm); Heavy Load on July 25 (noon). The band will play at 9pm. Heavy Metal will be released in selected cinemas on 12 September

Explore Film

• Film Reviews

• Trailers

• DVD

• London Film Festival

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010