The results of studies of the relationship between the ionic and electronic subsystems of metals are presented. The technique of thermo-EMF measurement on samples made of titanium alloy and steels is used. As shown, as a result of various methods of finishing treatments, the thermoelectric characteristics of metals change. The detected patterns can be used to optimize the processes of parts’ treatment and to select the part material for efficient operation under given load conditions. The results of the study suggest that the main influence on the thermo-EMF is determined by the value of the stress–strain state of the structure of the metal sample.