Rare earths are widely used in the metallurgical industry, accounting for about one-third of the total rare earth usage. Rare earth elements can easily react with oxygen and sulfur to form high melting point oxides, sulfides, and sulfur oxides with low plasticity at high temperatures. Adding rare earth elements to molten steel can help with desulfurization, deoxidation, and change the morphology of inclusions, improve the toughness and fracture properties of steel at normal and low temperatures, reduce the thermal brittleness of certain steels, and improve heating workability and the strength of welded parts. Rare earth elements are used as graphite spheroidizing agents, nucleating agents, and control agents for harmful elements in cast iron, which improve the quality of castings and greatly improve their mechanical properties. They are mainly used in four aspects: steel ingot molds, rolling mills, cast pipes, and special-shaped parts. In the application of non-ferrous alloys, it has a good effect on various alloys based on non-ferrous metals, improving the physical and mechanical properties of the alloys. More commonly used are aluminum, magnesium, and copper series.