Physical ideas about the mechanism of plastic deformation, its effect on the fine structure, structure and properties of metals and alloys are presented. Processes of return, polygonization and recrystallization at heating of cold-deformed metal are considered. The effect of thermal deformation is described taking into account the interaction of impurity atoms with dislocations, phase and structural transformations. The phenomenon of superplasticity is considered. Particular attention is paid to the hot deformation process. The analysis of phenomena underlying steel hardening as a result of thermomechanical treatment, including in controlled rolling, is given.