A new damage function suitable for metals under dynamic loading, based on the physical statistics of microvoids in metals and the law of conservation of energy, is presented in this article. This new damage model has a sound physical or theoretical foundation and fewer adjustable or empirical parameters than most existing models. Several hydrodynamic elastic-plastic numerical modeling experiments that use this damage function combined with the proper constitutional equations have been conducted by us and the results are in good agreement with previously published experimental results on different metals with different geometries. ©1997 American Institute of Physics.