Liquid metals remain of both fundamental and technological interest and the concepts needed to understand their properties are set out in this book, starting from a survey of the basic experimental facts to be explained. The quantitative theory of liquid pair correlation functions, effective ion-ion interactions, thermodynamic properties and electronic and atomic transport is then developed. The book goes on to discuss inelastic neutron scattering, critical behaviour, magnetism, the liquid/metal surface, binary liquid metal alloys, the two component theory of pure liquid metals, shock wave studies, liquid hydrogen plasmas and the constitution of giant planets.