Metal piping materials like copper and steel offer several advantages for HVAC applications, including high strength and durability, excellent heat transfer properties, and resistance to high pressures and temperatures. Copper is particularly well-suited for refrigerant lines due to its high thermal conductivity and resistance to corrosion. Steel piping is often used for larger HVAC systems due to its high strength-to-weight ratio and cost-effectiveness. However, metal piping materials can be heavier and more expensive than plastic alternatives, and may require additional corrosion protection measures.