An alloy is a metallic substance composed of two or more elements, as either a compound or a solution. Alloys are usually produced by melting the mixture of ingredients and are known to feature metallic bonding. They are combinations of metals or metals and other elements that are formed to impart certain properties to metals or to strengthen some of their existing properties. Alloys can either be solid solutions of metallic elements in which all the individual grains/crystals of the metals are of the same composition, or they can be mixtures of metallic phases featuring at least two different solutions, resulting in microstructures containing different types of crystals inside the alloy. The constituents of an alloy are measured in terms of their mass percentage, and alloys can be classified into two categories based on the arrangements of atoms in their respective lattices: substitutional alloys and interstitial alloys.

Some examples of alloys include brass, which is an alloy of copper and zinc, and bronze, which is an alloy of copper and tin/08%3A_Ionic_and_Metallic_Bonding/8.12%3A_Alloys). Steel is another important alloy that contains significant amounts of elements other than iron and carbon, such as chromium, nickel, manganese, molybdenum, silicon, tungsten, vanadium, and boron. Alloys are created by combining two or more metals or elements, and the resulting material typically has improved properties compared to its constituent parts. For example, steel is stronger and more durable than iron alone, and bronze is harder and more corrosion-resistant than pure copper.