The preparation of model systems based on thin epitaxial oxide films and oxide single crystals is discussed. A variety of surface sensitive techniques has been applied to study the geometric and electronic properties of these systems. The findings are correlated with adsorption and reaction of probe molecules on the surfaces. Metal vapor deposition under controlled conditions leads to the formation of metal aggregates with narrow size distributions. Their properties have been characterized, establishing that we can begin to bridge the materials gap between catalysis and surface science. While mainly performed under UHV conditions, adsorption measurements can be pushed to ambient conditions using non-linear optical techniques such as sum frequency generation. Results for systems with deposited metal aggregates will be discussed.