Friction stir processing (FSP) has emerged as a prominent technique for producing surface composites in a solid-state manner. Over the past two decades, FSP has demonstrated significant advancements in microstructural modification and surface composite fabrication. Surface composites of lightweight alloys, such as magnesium alloys, offer several advantages, such as low density and high strength. Magnesium alloys’ AZ series are extensively used in lightweight structures and have the potential to provide tailored solutions for a variety of industries. The article explores the operational mechanisms of surface composites, including the parameters’ influence on the surface composite qualities. Furthermore, an in-depth review of the latest developments in AZ31 alloy-based magnesium surface composites using FSP is provided.