Thin metal films on oxide substrates are used in a variety of technological applications including microelectronic devices, catalysts and sensors. Ideally, the films should have low defect densities. This prerequisite can often be fulfilled by growing epitaxial films. Recently, epitaxial films have received a great deal of attention for fundamental studies of the structure and bonding of heterophase interfaces. In this paper, fundamental investigations of the interface formation for MBE deposited metals (Cu, Nb, V) on TiO2 single crystals (rutile) will be presented. The structure and chemical composition of the metal/oxide interfaces were determined by a variety of surface science and transmission electron microscopy methods. We conclude on general trends, which allow the prediction of the growth behavior of metals on oxides as a function of processing and material parameters.