The melting of metal nanoparticles is considered in the framework of the Landau mean-field model. For the definition of the order parameter, the Lindemann criterion is employed. The phenomenological principle, implying that surface layer of nanoparticles can be in metastable states indefinitely, put forward to explain the formation of pseudo-crystal line surface layer. Therefore, the metastable states of bulk crystal correspond in structure to the stable states of surface layers under relevant conditions. It is shown that all metastable states are classified by values of the order parameters. The critical radii are determined. The present model elucidates that the metastable states of bulk metals are in a direct connection with the structure states of nanoparticles surface layers. The dependency of the Landau phenomenological coefficients on the size of small particles is under consideration. The developed model is appropriate for nanoparticles, nanowires, and thin films. It allows one to account for influence of matrix. The comparison with available experimental data is carried out. (C) 2008 Elsevier B.V. All rights reserved.