The electronic properties of transition metal oxide (TMO) films in resistance random access memory (ReRAM) devices have been gaining research interest in relation to their relevant application in the field of non-volatile memory devices. TMO films sandwiched between two metallic electrodes in ReRAM devices have the ability to switch its electronic properties between insulator and metal upon being subjected to pulse voltages. However, this switching mechanism has not been fully clarified. As part of this big endeavor to fully elucidate this switching mechanism in ReRAM, we introduce, in this review, the proposed effect of electric field on the metal electrode-TMO interface's electronic properties. We use the Ta/CoO/Ta system in our investigation and evaluated its density of states (DOS) to analyze changes in the bandgap of the interface layers in the presence of an electric field. Analysis shows that the presence of the electric field causes a change in the bandgap of the TMO interface layer near the anode side while no change have been seen at the interface layer near the cathode side. This presumes that the anode side has an important role in switching mechanism as compared with the cathode side.