The wetting and spreading of liquid Ag drops on Cu (001) surfaces are studied with molecular dynamics simulations. As the liquid Ag drop spreads on the Cu surface, reactive wetting occurs in that a Ag/Cu alloy is formed. The results for the reactive wetting case are compared to a frozen substrate for which there is no alloying. At the highest temperature studied, T = 1300 K, the radius of the drop spreads faster than for the frozen substrate, indicating the driving force for spreading is greater when the liquid and solid mix. Lowering temperature in reactive systems results in behavior more similar to non-reactive systems due to suppressed mixing.