Rock 'n' roll icons U2 descend onto the red carpet in Toronto on Thursday for the premier of From the Sky Down, the first documentary to open the Toronto International Film Festival in its 36-year history.

The festival, a widely-watched event often seen as a starting point in the movie industry's annual Oscar race, features a long list of Hollywood royalty, from Brad Pitt and George Clooney to Keira Knightley and Glenn Close.

But musicians also play a prominent role in the 11-day event known as TIFF.

Rock documentaries about Pearl Jam and Neil Young are getting top billing, and the appearance of U2 members Bono and The Edge has made Thursday's opening night screening the hottest ticket in town.

The U2 film takes a look back at the struggles the Irish super-group had when making their 1991 album Achtung Baby, which was seen as a daring reinvention of the band following the huge success of 1987's Joshua Tree and 1988's somewhat less-well received Rattle and Hum.

It was them at their very highest highs and their very lowest lows, director Davis Guggenheim told Reuters.

U2 guitarist The Edge appeared in Guggenheim's 2008 documentary, It Might Get Loud, alongside Led Zeppelin's Jimmy Page and the White Stripes' Jack White.

That led to Guggenheim being asked to make From the Sky Down, a film in the mold of the Bruce Springsteen documentary The Promise and The Rolling Stones' Exile in Main Street, which looked back at important albums 20 years later.

There comes a time when it is dysfunctional not to look into the past, U2 frontman Bono says in the background of the film as the band is about to play the Glastonbury Festival for the first time earlier this year.

TIFF'S HIGH-PROFILE DOCS

From the Sky Down is just one of a number of high profile documentaries at TIFF this year that offer audiences a look into personalities like Sarah Palin, a murderer on death row, and comic book fanatics. There's also a 15-hour epic that chronicles the history of film.

It's the most exciting time for documentaries, said Guggenheim, whose 2006 global warming film 'An Inconvenient Truth' won the Academy Award for best feature documentary.

I think that the form is exploding and evolving and mutating in wonderful ways, whereas feature films, I think they're kind of stuck.

'From the Sky' down is Guggenheim's third movie to show at TIFF. It's such a great festival, he said. It's a great place to go to remember why you make movies.

Documentaries won't be the only films at TIFF. Clooney will turn out for The Ides of March, that he directed and stars in, as well as The Descendants, in which he portrays an indifferent husband and father forced to reexamine his life.

Pitt stars in Moneyball, based on the true story of Billy Beane, a professional baseball manager who reinvents his team, while David Cronenberg's A Dangerous Method, starring Viggo Mortensen and Keira Knightley, will be tested for audience reaction after runs at other festivals.

Eyes will also be watching Glenn Close in Albert Nobbs, a drama the five-time Academy Award nominee co-wrote in which she plays a woman pretending to be a male butler set in 19th century Ireland.