The effects of the annealing procedure at 400–450 K on the electronic properties of nanoscale thin films of Ca, Au and Ag grown on Cu(1 1 1) at room temperature were probed by high-resolution electron energy loss spectroscopy measurements. Ca surface plasmon underwent to a significant red-shift upon annealing, due to the oxidation of the topmost Ca layer. Water strongly interacted with the CaO interface at room temperature. Au surface plasmon disappeared upon annealing the gold film, as a consequence of the formation of an Au–Cu alloy. Ag surface plasmon red-shifted both in the annealed adlayer and with increasing temperature compared with the frequency recorded for the as-deposited silver film.