Three iconic rock guitarists from successive generations—Jimmy Page of Led Zeppelin, the Edge of U2, and Jack White of the White Stripes—meet for a musical summit in this engaging, if inherently contrived, rock documentary. Filmmaker Davis Guggenheim (An Inconvenient Truth) shows how each man bonded with his instrument and broke with the prevailing sounds of the day, and there are revealing glimpses of the players’ practice spaces and other locales that figured in their careers (the country house where Page and company recorded Led Zeppelin IV, the secondary school where the teenage members of U2 first rehearsed). The strain to pull all this together becomes more evident as the movie progresses, and the three-way musical finale, a rickety acoustic run-through of “The Weight,” hardly lives up to the stars’ reputations. But guitar heroes, real or imaginary, will think they’ve died and gone to heaven. PG, 97 min.