Metallurgical coal, also known as "coking coal," is a name for bituminous coal that is very low in ash and sulphur content, and is thus especially suitable for being distilled into coke, which is a crucial ingredient in the production of steel.
Since metallurgical coal is rarer than other forms of coal, it typically sells for a higher price. However, since its primary use is in the steel industry, the market for metallurgical coal tends to rise and fall with the price of steel.