Biodegradable magnesium (Mg)-based medical devices have revolutionized medical implants by uniquely combining biocompatibility and mechanical strength. Fully degradable Mg-based implants have been developed to provide temporary structural support and serve as a dynamic scaffold for tissue repair and restructuring. Additionally, Mg-based devices can respond to physiological signals, and their integration with electrical currents or pulses has been explored to enhance tissue healing and functional recovery. This review provides a comprehensive overview of the development and application of Mg-based medical devices, highlighting their evolution from traditional orthopedic, vascular, and dental uses to advanced systems that actively modulate physiological processes—a shift from passive support to active modulation. The application range of Mg-based devices has expanded from early vascular sutures, bone screws, and stents to multiple clinical fields including porous bone repair scaffolds, anastomotic staples, bioactive devices, and electro-active systems. Bioactive Mg devices demonstrate therapeutic properties including antibacterial, anti-inflammatory, anti-tumor, and osteogenic functions through their degradation products, while electro-active devices utilize the electrical properties of Mg for sensing, monitoring, and therapeutic stimulation. Finally, this review highlights current challenges, including maintaining mechanical support performance, optimizing control of biochemical reactions, and balancing electro-regulatory functions, and identifies future research directions aimed at enhancing the clinical application of biodegradable Mg-based implants, thereby contributing to the significant advancement in the biomedical field.