In this talk, I will address the mechanism for the charge transport at molecular interface showing dual functionality (i.e., rectification and conductance switching at the same time) which can potentially function as next-generation electronic devices (e.g., a selector-free molecular memory device or an artificial synapse). The molecular interface is composed of alkanethiolates terminated by a bipyridine (BIPY) group complexed with transition metal ions. The hysteresis of conductance shown in these BIPY-MCl2 junctions changes upon the metal ion and the voltage applied to the junction. The hysteretic behavior of conductance in these junctions appears only in the incoherent Fowler-Nordheim (FN) tunneling regime. Using this correlation, the conductance characteristics of BIPY-MCl2 junctions can be controlled. This voltage-induced change of conductance demonstrates a simple, fast, and reversible way to modulate conductance in molecular tunneling junctions.