Novel properties found in the atom-thick metal overlayed semiconductor systems motivate the studies on the two-dimensional metal films. In this work, the electronic structures of Ce overlayer on a Si substrate have been studied by using first-principles approach. Monoatomic-thick Ce layer on Si(111) surface exhibits metallic behavior and ferromagnetic ordering with weak induced magnetic moments of the Si atoms in the first Si bilayer. Our results reveal the intralayer metallic bonding and the mixed covalent and ionic characteristic of the interfacial bonds in Ce-Si(111). The bonding picture is similar to that of the superconducting monolayer metals on Si(111) surface found in experiments, and elucidates the two-dimensional metallic nature of Ce overlayer with anisotropic band structures in the Ce-Si(111) interfacial systems. (C) 2017 Elsevier B.V. All rights reserved.