It is important to analyze the electronic state of interface in search of the best buffer-substrate combination. We have studied the electronic state of metal (Ag, Cu, Ag-Cu alloy, Ni)-MgO interface by using DV-Xα method. The calculation model consists of interface between MgO and metal clusters. We calculated the density of states (DOS), the charge-density distribution, and the effective charge, and examined the electronic interaction at the interface. We found importance of the covalent (metallic) bonding between metal atom and Mg as compared with ionic contribution between oxygen and metals. Such bonding becomes stronger in order of Ni>Cu>Ag, suggesting that Cu alloying may be effective for stronger electronic coupling of Ag substrates.