In this article, the theory of chemical bonding, developed based on the author's theoryof compressible oscillating ether, is applied to the analysis of the interaction of valenceelectrons of atoms in the metallic crystal lattices of Group I metals and the molecularcrystal lattices of Group VII halogens. It is demonstrated that the valence electrons ofmetals are weakly bound by their intersecting parts, which ensures the stability of themetals' crystal structure and proves the existence of a current in a conductor in the formof a directed wave of disturbances of interacting valence electrons, traveling at thespeed of light along the conductor's metallic lattice. This refuses the conclusions ofmodern quantum band theory of solids regarding the causes of metal electricalconductivity. It is also demonstrated that the valence electrons of diatomic halogenmolecules (except iodine) located at adjacent sites of molecular crystal lattices do notintersect, which excludes the possibility of an electric current wave passing through sucha molecular crystal lattice. The causes of the electrical conductivity of solid crystallineiodine are elucidated.