By using the classical nucleation and growth dynamics to describe the melting process of superheated solid materials induced by ultrafast laser pulse irradiation, we found that the melting process of highly superheated solid materials is governed by explosively homogeneous nucleation. For the superheating degree of 1.6-1.9, the melting time for aluminum is several tens of picoseconds. In this case the lattice is heated within a few picoseconds, thus the total melting time of the solid materials is governed by the explosively homogeneous nucleation. However, for the very short laser pulse irradiation, such as femtosecond laser pulses with high fluences, the nonthermal mechanism plays a critical role in the melting process, and the classical homogeneous nucleation theory and growth dynamics is not useful. That is to say, the classical homogeneous nucleation theory and growth dynamics is useful for describing the rapid thermal melting process, however, is not suitable for explaining the nonthermal melting process. (C) 2004 Elsevier B.V. All rights reserved.