The tutorial covers the thermodynamic description of one-, two-, and three-component metal systems in the liquid state. Basic methods of experimental study of thermodynamic properties of liquid alloys are described. Structure and thermodynamic properties of individual liquid metals are considered. The relationship between the phase diagram and the thermodynamic properties in the liquid state of double metal systems is discussed. Particular attention is paid to systems with the formation of intermetallic compounds, their structure and properties in the liquid phase.