The spectrum of a photoexcited electron pair carries detailed information on the electron-electron interaction in metals. This is deduced from the results of a theoretical model presented here for the treatment of the double-photoelectron emission from surfaces. Main features in the two-particle spectra are assigned to (a) the exchange-correlation interaction, (b) the electronic band structure, (c) the photoelectron diffraction, and (d) the specific experimental setup. Comparison with experiments is made and common features and differences to the atomic case are pointed out.