It is demonstrated that, by taking the solid metal at zero temperature as the references state, the enthalpy of formation of homonuclear diatomic molecules can be obtained as the surface energy of a piece of metal having the size of two atoms. It is suggested that the energy of larger homonuclear metal clusters can be derived similarly.The heat of formation of heteronuclear diatomic molecules, relative to the two pure metal dimers, is derived by means of a model description for the interaction energy which is very similar to that used for interfacial energies and alloy heats of solution in the condensed phase.