The scanning tunneling microscope is not only a well‐established tool for a topographic characterization of the sample surface on the atomic scale. It also provides a variety of spectroscopic techniques to examine electronic, magnetic, vibrational and optical properties of a localized system. The following presentation gives an overview, how scanning tunneling spectroscopy, inelastic electron tunneling spectroscopy and photon emission spectroscopy with the STM can be employed to investigate spatially confined metal systems and their interaction with molecular gases. The experiments were performed on single Pd and Au atoms, mono‐atomic chains and individual Ag clusters on a NiAl support and a Al2O3thin film. © 2003 American Institute of Physics