We describe the oxidation of 1000 Å thick metal films on glass substrates when exposed to a scanning laser beam. For Cd and Cu films optical spectroscopy shows an energy gap of 2.45 eV and 2 eV respectively, in agreement with published data for CdO and Cu2O. We measure the power threshold for complete oxidation in a single scan and deduce the maximum temperature, which is inconsistent with thermal oxidation data but corresponds to the m.p. of the metals. We point out the important contribution of the heat of formation to the temperature balance and demonstrate that in the case of Al this effect is sufficient to destroy any oxide formed.