The atomic structure and diffusion at the solid-liquid heterophase interface are investigated by using Molecular Dynamics. The system studied is made of crystalline copper with surface terminations (100) and (111) and liquid aluminum, both modeled via adapted n-body potentials from the literature and cross interactions obtained by fitting the mixing enthalpy of the two species to experimental values. It is shown that at the interface the liquid forms layers with spacing such that the local average density equals that of the bulk liquid. The interfacial liquid is layered whatever the surface orientation is even if the solid is reduced to a single crystalline or amorphous layer, in agreement with density functional theory. Layering is however suppressed at the interface between the liquid and a bulk amorphous solid with a rough surface termination. Surprisingly, diffusion in the interfacial layers proceeds via vacancies, which also accommodate the density misfit between solid (Cu) and liquid (Al). These results are further discussed in the frame of existing experimental and theoretical works.