This lecture covers selected aspects of the surface chemistry of porphyrins, phthalocyanines, their metal complexes, and related compounds, with particular focus on chemical reactions at solid/vacuum interfaces. Porphyrins are not only important biomolecules, they also find, together with the artificial phthalocyanines, numerous technological and scientific applications, which often involve surface and interface related aspects. After a brief summary of fundamental properties of these molecules in the context of surface science, the following topics will be discussed: (1) Aspects of geometric structure, including self-assembly, conformation, mobility and manipulation of the adsorbed molecules. (2) Surface-related changes of the electronic structure. (3) The role of the metal center in the surface chemical bond. (4) On-surface coordination reactions, such as direct metalation and coordination of axial ligands. (5) The influence of axial ligands on the surface chemical bond.