Lars Ulrich has heaped praise on a disabled fan who made a movie about his attempts to meet Metallica, calling the documentary "deeply moving."

Rock devotee Tom Spicer - who suffers from Fragile X syndrome, a condition which causes intellectual disabilities - teamed up with his journalist sister Kate to track down the metal band for the chance to talk to his favourite member, Ulrich.

The siblings recorded their efforts for poignant new film "Mission To Lars," which the drummer has hailed as "a great testament to the importance of music."

He says, "I thought the film was deeply moving. Meeting Tom and Kate, when they came out to film, it was an experience in itself. But seeing the film and reconnecting with the team was another experience."

"It's not something we're directly involved in - it's their film, their journey. But we're supportive of their endeavour. We don't want to take it over and have it turn into some kind of vanity project."

"It's a great testament into a world I didn't know much about and a great testament to the importance of music and what it means to different people."