Short answers, pulled from the story.
Metallurgical coal is used to produce coke, which serves as an essential fuel and reactant in the blast furnace process for primary steelmaking. The demand for metallurgical coal moves closely with global steel demand.
Metallurgical coal produces coke when heated in a low-oxygen environment; thermal coal does not. Because of that difference in end-use, prices for the two types of coal are usually quite different.
Metallurgical coal comes mainly from Canada, the United States, and Australia. Australia leads the seaborne trade, handling 58% of internationally shipped metallurgical coal, with most exports going to China.
Between 2007 and 2018, metallurgical coal and coal for other uses such as heating accounted for 7% of total U.S. coal consumption. The electric power sector consumed the remaining 93%.
There are four main grades of metallurgical coal: hard coking coal (HCC), medium coking coal (MCC), semi-soft coking coal (SSCC), and pulverized coal for injection (PCI) coal. Each grade differs in how well it performs when converted to coke.
Primary steelmaking companies often maintain coal-producing divisions to ensure a stable and low-cost supply of coking coal. Vertical integration of this kind reflects how central metallurgical coal is to the primary steelmaking process.