Resistance random access memory (ReRAM) is emerging as a next-generation nonvolatile memory. One of the most promising materials for the ReRAM application is a composite of a reactive metal [such as aluminum (Al)] and a mixed-valance manganite [such as La(1-x)Ca(x)MnO3 (LCMO) and La(1-x)Sr(x)MnO3 (LSMO)]. One of the current hypotheses regarding the origin of the resistive switching of such systems is a voltage-controlled reversible formation of a high-resistance aluminum oxide (AlO(x)) layer at the Al/LC(S)MO interface through oxygen migration from LC(S)MO. To validate this hypothesis, quantum mechanics (density functional theory) calculations were carried out on an atomistic model of the resistive-switching phenomena at the Al/LSMO interface (the composite systems of Al/LSMO and AlO(x)/LSMO) as well as on the component materials such as Al, AlO(x), LaMnO3, LaMnO(3-delta), La(1-x)Sr(x)MnO3, and La(1-x)Sr(x)MnO(3-delta). The changes in the structure, energy, and electronic structure of these systems during the oxygen vacancy formation in LSMO, the oxygen migration through the Al/LSMO interface, and the AlO(x) formation were investigated.