The term KETTLE MATERIAL can be solved by the 6-letter word COPPER. COPPER is a reddish-brown metal that has been used for thousands of years in many different applications. It is a malleable and ductile metal, meaning it can be easily shaped and bent, making it an ideal material for kettles. COPPER is also a great conductor of heat, which makes it an excellent choice for kettles as it allows for efficient and even heating.