The thermodynamics of a solid metal electrode in contact with a liquid electrolyte are briefly reviewed. The contribution of the metal to the interfacial tension gamma and stress g are calculated within the jellium model. When the electrostatic terms are excluded, both quantities vary smoothly with surface charge density. Over the investigated range, the variation of the surface stress is much larger than that of the interfacial tension. The contribution of an adsorbate to gamma and g is considered within the lattice gas model, which is treated in the mean-field approximation. While the interfacial tension is governed by the familiar electrocapillary equation, the surface stress depends on the energy of adsorption and on adsorbate interactions. In simple cases the surface coverage and the interfacial stress show a similar dependence on the electrode potential, and the variation of the stress resembles a cyclic voltammogram.