The theory regarding the degenerate electronic gas inside an electron-conductor producing an electronic gas, i.e., the surface-electrons, covering the surface of the conductor is applied to the ordinary and the selective photo-effect and the evaporation from heated metals. Further, it is explained how the adsorption caused by metallic surfaces and the catalytic effect produced by them can be calculated when surface-electrons are considered and that the potential barrier which accounts for the work function also can be estimated.