A model for the calculation of excitation energies of molecules close to a metal surface is presented. The molecule is treated at the density functional theory (DFT) or Hartree-Fock (HF) level and the excitation energies are calculated through a time dependent DFT (TDDFT) or time dependent HF (TDHF) procedure. The metal is treated as a continuous body characterized by its frequency dependent dielectric constant, taken from experiments, in the case modified to take into account nonlocal effects in the response to the metal. Such effects are accounted for by using the specular reflection model and a hydrodynamic correction to the dielectric constant. The presence of a solvent is described with the Polarizable Continuum Model. The (quasi-)electrostatic interactions between the molecule and the metal-solvent environment are treated by exploiting the integral equation formalism, numerically solved through a boundary element method. Applications of the method are given to show its numerical accuracy and the dependence of the results on the various parameters of the model (e.g., nature of the molecule, solvent, chemical nature of the metal, metal-molecule distance).