Polymer composites are increasingly utilized in both high-structural and biomedical applications due to their high strength-to-weight ratio, design flexibility, and customizable properties. In demanding applications, ranging from load-bearing componenets to medical implants, ensuring long term durability and functional performance is essential. However, exposure to environmental stressors such as moisture, chemicals, UV radiation, and body fluids can degrade surface integrity and compromise composite performance. To address this, epoxy resins are employed as protective surface coatings owing to their excellent adhesion, chemical resistance, and mechanical robustness. Additionally, epoxy systems can be engineered to support biocompatibility and functional integration with biological tissues. Microwave-assisted curing of epoxy coatings presents a fast, energy-efficient alternative to conventional thermal methods, enabling uniform cross-linking, reduced processing time, and enhanced material properties. This chapter explores the role of epoxy coatings and microwave curing in extending the performance, longevity, and application range of polymer composites for both structural and healthcare-related uses, with attention to emerging smart and bio-functional coating systems.