The development of metal deactivator additives for the petroleum industry is reviewed from the first additive used in gasoline to the present. The chemistry of how these additives are thought to work is detailed and related to chemical structure. Discussions of the three classes of action attributed to metal deactivators: chelation, surface passivation, and bulk phase reactivity, are provided. In this regard special emphasis is given to the metal deactivator N,N'-disalicylidine-1 2-propane diamine (MDA) in aviation turbine fuels. Previously reported work, especially work from 1991 to the present, investigating the impact of MDA on jet fuel thermal stability is reviewed. A discussion of the six classes of metal deactivators most commonly found in the literature is also provided.