The structure and thermal properties of molybdenum nanoparticles are investigated by molecular dynamics simulation. Specifically, the solidification of molybdenum nanoparticles from liquid droplets at various cooling rates is performed to discuss the variety of nanoparticle structures with 54 to 16000 atoms. Bcc single-crystalline and glassy nanoparticles are formed at cooling rates on the order of 10¹⁰ and 10¹³ K/s, respectively, for all sizes of nanoparticle except for the smallest cluster, Mo₅₄. In addition, a polycrystalline structure is formed in nanoparticles with 2000 atoms or more at intermediate cooling rates on the order of 10¹² K/s. On the other hand, a fivefold rotationally symmetric Mo₅₄ cluster is formed at low cooling rates. The solidification point decreases with increasing cooling rate for all nanoparticles considered. At a constant cooling rate, the depression of the solidification point is proportional to the inverse of the cube root of the number of atoms in the nanoparticle even for the highly symmetric cluster consisting of only 54 atoms.