Peculiarities of metal wire explosion by high voltage loading are investigated. Embedded atom method is employed to calculate atomic interaction. In this work, cylindrical specimens of polycrystalline copper are examined. High-rate heating of specimens induced by high-density electric current is simulated by scaling the velocities of atoms. It is demonstrated that simulated specimen destruction caused by high-rate heating leads to formation of vapor phase and clusters of various sizes. Simulated system behavior during explosion is determined by processes of destruction and cluster agglomeration, surface atom evaporation, cluster collision, and atom deposition on clusters free surfaces. Influence of the grain boundary region on processes of destruction and formation of clusters with internal block structures is revealed. It is proved to be the case of nonuniform distribution of electric current density (temperature) on the stage of high-rate heating.