Energy distributions of H atoms resulting from grazing scattering of H-2(+) from metal surfaces are calculated analytically and by using classical trajectories simulations. The main mechanism leading to dissociation of H-2(+) is proposed to be dissociative capture of an electron from the metal into the antibonding state of the H-2 molecule. It is shown that the energy distributions of scattered atoms yield information of both the molecular axis orientation and the vibrational excitation of the molecules during the scattering process.