The self-assembly of large organic molecules has become a vividly explored and interdisciplinary field in science. One major goal is the tailored fabrication of highly ordered, molecular networks, which are stabilized on a metal surface. Metalloporphyrins receive particular attention, because their distinct intrinsic functionalities make them promising candidates for applications in chemical sensors, solar cells, and for tailored catalytic processes. Based on scanning tunneling microscopy investigations, several novel and fundamental contributions are presented, which has led to a new level of understanding. Highlights are the results with respect to intramolecular conformation and supramolecular ordering, electronic interactions with the substrate, surface confined synthesis such as in-situ metallation reactions, and ligand effects.The number of publications this work has led to emphasises its quality and significance.