Shock adiabats of metals with different initial volume and pressure have been calculated with the use of multi‐phase equation of state. The stability of shock wave has been investigated with the use of known criteria. We found two types of instabilities occurring in the vicinity and inside two‐phase liquid‐gas region. They are the specific sound instability arising as a spontaneous sound emission from the shock discontinuity and two‐wave configuration. The position of the instability region and its dependence on initial pressure and volume has been analyzed. Discussed are general regularities obtained on the base of the analysis for 30 metals. © 2004 American Institute of Physics