  The frequency spectrum of the finite temperature correction to the Casimir
force can be determined by the use of the Lifshitz formalism for metallic
plates of finite conductivity. We show that the correction for the TE
electromagnetic modes is dominated by frequencies so low that the plates cannot
be modelled as ideal dielectrics. We also address the issues relating to the
behavior of electromagnetic fields at the surfaces an within metallic
conductors, and claculate the surface modes using appropriate low-frequency
metallic boundary conditions. Our result brings the tehrmal correction into
agreement with experimental results that were previously obtained.
