Analytical models for size-dependent melting temperature T-m(D), melting enthalpy Delta H-m(D), and surface energy gamma(sv)(D) of metallic nanowires have been proposed in terms of the unified nanothermodynamical model where D denotes the diameter of nanowire. As D decreases, T-m(D), Delta H-m(D), and gamma(sv)(D) functions are found to decrease almost with the same size-dependent,trend. Due to the inclusion of the effect of dimensionality, the developed model can be applied to other low-dimensional systems. It is found that the ratio of depression of these thermodynamic parameters for spherical nanoparticle, nanowire, and thin film is 3:2:1 when D is large enough (> 20h with h being the atomic diameter). The validity of the model is verified by the data of experiments, molecular dynamics simulations, and other theoretical models.