The volatility of the tetrachloride and tetraiodide complexes of Ti(IV) is exploited in the purification of titanium by the Kroll and van Arkel–de Boer processes, respectively.
Metal halides act as Lewis acids. Ferric and aluminium chlorides are catalysts for the Friedel-Crafts reaction, but due to their low cost, they are often added in stoichiometric quantities.
Chloroplatinic acid (HPtCl) is an important catalyst for hydrosilylation.