Halogens, in particular fluorine atoms, are favorite tools to fine-tune the chemical and biological properties of pharmaceutical or agricultural development products. At the same time, such an electronegative substituent can effectively assist the site-selective functionalization of an aromatic or heterocyclic core compound by directing a metal to the targeted position, the metal acting as a harbinger for the definitive substituent. The concept is illustrated by typical examples selected from the carbazole, indole, pyrrole, pyrazole, imidazole, pyridine, quinoline and pyrimidine fields.