The formation of solvated electrons at metal electrolyte interfaces is discussed. It is suggested that hydrogen molecules may be formed at an interface, without the prior formation of hydrogen atoms, by the reaction The evolution of hydrogen by this reaction, both electrolytically and spontaneously during the dissolution of a metal, is discussed. For metals which form hydroxides of low solubility, it is proposed that the hydroxyl ions produced by this reaction form a film across the metal surface and that it is the dissolution of this film which determines the characteristics of the hydrogen evolution process. Calculations of the rates of dissolution of iron in reducing acids made on the basis of this model show good agreement with experimentally observed rates. In addition the activation energies for the dissolution of the hydroxide film on iron and mercury, estimated from the dissociation constants of the hydroxides, are 11.4 and 19 kcal/mole, respectively. These values compare favorably with the observed activation energies for the dissolution of iron, 11.5 kcal/mole, and for hydrogen evolution at a mercury surface, 22 kcal/mole.