As the primary method of obtaining metallic copper resources from copper ore, pyrometallurgical smelting usually produces a large amount of copper slag, which has good physical properties and contains many valuable metals. Therefore, how to fully recycle and utilize it has become a research direction that has received much attention in recent years. To better understand the ‘artificial’ ore of copper slag, this article reviews the copper smelting process, the sources and properties of copper slag, and its resource potential. It introduces the method of recovering valuable metals from copper slag, including pyrometallurgical impoverishment, hydrometallurgical recovery, mineral processing methods, etc. Furthermore, it lists some applications of copper slag in the field of materials, primarily in cement, concrete aggregates, and glass-ceramic materials. Finally, based on the sustainable development background, copper slag’s efficient recycling is prospected. However, scalable, eco-friendly recovery technologies remain limited and warrant further research.