This lecture covers the recycling of metals, energy model, and the challenges associated with metal extraction and conversion. It discusses the composition of Earth's crust, metal properties, extraction methods, and the energy requirements for primary and recycled aluminum production. The instructor explores the energy embodied in aluminum, the dynamic material flow analysis, and the energy model for producing and using metals. The presentation also delves into the energy efficiency of metal recycling, the limitations imposed by social behavior and recycling technologies, and the importance of a life cycle approach in metal recycling.