Publisher Summary Metallurgical coke, along with iron ore and limestone, is layered into a blast furnace to convert the iron ore to metallic iron. Coke, which is mostly carbon, reacts with the blast air to produce carbon monoxide, which, in turn, reacts with the iron oxide to produce carbon dioxide and metallic iron. This chapter details the coal-to-coke transformation, which is the most successful industrial applications of coal petrology in the carbonization industry. Coal petrology is used to evaluate the suitability of a given coal for coking, predict the strength of cokes made from both single coals and coal blends, predict peak coking pressures, predict coke reactivity, evaluate the nature of quinoline insolubles in coal tar pitches, detect weathering in coal, and evaluate petroleum cokes. The petrographic characteristics of metallurgical coke reveal much about its composition and structure and can be used to evaluate its behavior and formation.