Metals are natural elements found on the Earth that are mined and formed into different shapes and sizes. They conduct heat and electricity and are easy to shape and form. Aluminum is lightweight, resists corrosion, and used for various building and manufacturing applications. Stainless steel resists corrosion, and carbon steel is durable for general applications. Alloy steel is combined with other materials to increase its strength and hardness. Tool steel retains its cutting edge and shape at high temperatures and resists abrasion. Brass resists corrosion and is often combined with other metals for specific applications. Bronze is made of copper and tin and has a patina finish that withstands harsh outdoor conditions and elevated temperatures. Copper resists corrosion for many industrial applications. Titanium has the highest strength-to-weight ratio of any element. Cast iron is strong and resists shocks and wear. Nickel is weldable, corrosion resistant, and remains strong and ductile at high and low temperatures.