We examine the direct contribution of the metal to the differential capacitance of an ideally polarizable electrode. We discuss the extension of the jellium model to the case of noble metals. A simple and rather realistic model is proposed for describing the electronic structure of these metals. We check this model by investigating the electronic work function and its variation with the cristallographic orientation of the surface. Satisfactory results are obtained. As a first step in the calculation of the capacitance we study the response of the metal to an external charge. We may conclude that the metal has certainly a large contribution to the capacitance. Moreover, the correct variation of the capacitance with the orientation of the surface is predicted although the absolute determination of the capacitance seems to be extremely difficult.