This review analyzes current ideas on the electrical conductivity and galvanomagnetic properties of normal pure metals, in which relaxation processes are governed entirely by collisions of electrons with phonons. Attention is concentrated on a group of closely related topics: the diffusive nature of electron motion on the Fermi surface at low temperatures, mutual influence of the normal collisions and of the umklapp processes, and dependence of the relaxation mechanisms on the topological properties of the Fermi surface. The analysis is based on the diffusion equation method which makes it possible to treat in a unified manner all the topics under discussion and to formulate the results in terms of specific physical mechanisms.