This lecture covers the fundamentals of steel metallurgy, including an overview of selected high-performance steel classes such as stainless steels, steels for elevated temperature applications, advanced high strength steels, FeMnSi-based shape memory alloys, and the steelmaking process. It also discusses the importance of steels, the steel classification based on carbon content and alloying elements, the role of alloying elements in steel, phases in steel, and the heat treatment of steels.