The reactions of manganese and iron monoxides (MnO and FeO) with methane molecules have been investigated using matrix isolation infrared absorption spectroscopy. The metal monoxide molecules were prepared by laser ablation of MnO2 or Fe2O3 targets. The reaction products were identified on the basis of isotopic substitution experiments with (CH4)-C-13 and CD4, as well as density functional theoretical calculations. In solid argon, manganese and iron monoxides reacted with methane spontaneously on annealing to form the OMn(CH4) and OFe(CH4) complexes, which were predicted to have C-2v symmetry with the metal atom coordinated to two hydrogen atoms of the methane molecule. The OMn(CH4) and OFe(CH4) complexes underwent photochemical rearrangement to the CH3MnOH and CH3FeOH molecules upon ultraviolet irradiation.