First-principles calculations for several aromatic molecules with anhydride and thio groups on Ag (111) and Au (111) reveal that the self-assembly structures and the interface properties are mainly determined by the functional groups of aromatic molecules.Detailed investigations of the electronic structures show that the electrons in molecular backbone are redistributed and charge transfer occurs through the bond between the metal and the functional groups after these molecules have been deposited on a metal substrate.The interaction between Ag (111) (or Au (111)) and aromatic molecules with anhydride functional groups strengthens the π bonds in the molecular backbone,while that between Ag (111) (or Au (111)) and aromatic molecules with sulfur weakens the π bonds.However,the intrinsic electronic structures of the molecules are mostly conserved.The large-sized aromatic backbone has less influence on the nature of electronic structures than the small-sized one,either at the interface or at the molecules.These results are useful to build the good metal-molecule contact in molecule-based devices.