Metals are a class of elements characterized by a tendency to give up electrons and by good thermal and electrical conductivity. At room temperature and normal atmospheric pressure, metals tend to be solids - except for mercury, which is a liquid. Along with this, metals are usually ductile, malleable, shiny, and can form alloys with other metals. Some common metals are iron (important for steel), aluminum, and copper. Metals are tremendously important to a high energy society: they transport electricity in the electrical grid, and provide many services.
Aluminum alloy power lines.
Zirconium alloy for nuclear fuel bundles.
Steel building frame.
Generally, metallic elements are not found as isolated atoms, and instead group together into larger structures. These structures resemble large, extended sheets with a repeating pattern in how the atoms group together. It is this sheet-like structure that makes metals so useful, allowing them to be pressed into sheets that are used in building cars, containers, and even jewelry. In general, metallic atomic structures are highly organized and layers of these atoms stack to form a three-dimensional solid.
Unlike certain diatomic molecules - like molecular hydrogen or molecular oxygen - metals stay together because inside of the metal the electrons flow freely in a type of "electron sea" instead of sharing electrons between atoms. These electrons float freely around the nuclei inside of the metal. This free flowing "electron sea" explains why metals conduct electricity so well, as the movement of electrons produces a current, and there are so many electrons that are free to move inside of metals.
Metals are necessary to maintain society's modern standard of living. This demand contributes to energy demand because the extraction and processing of metals is extremely energy intensive. A significant fraction of the world's energy supply go into the mining of metals and turning them into useful products in the modern world. Since there is so much energy involved in metal processing, they have an incredible amount of embedded energy. Aluminum, in particular, requires a significant amount of energy to extract and process. When countries are modernizing their economies - in places like BRIC or N11 countries - large amounts of energy are invested to obtain metal for rapidly increasing infrastructure.
Metals are an important resource for the world today with almost countless applications. The electrical grid couldn't exist without copper and steel. In fact all areas of electricity production and distribution require metal, from turbines used to transform mechanical energy into electricity to the distribution stations that bring electricity to homes.
In addition to the electrical grid, metals are a principle component building construction (often in the form of steel reinforcement for concrete). Most vehicles are made from metal, from automobiles to airplanes. Common household appliances and electronic devices also use a significant amount of different metals as well. As technology advances, the number of elements used in society (including metals) increases.
For more information on how the unique properties of metals are used, see:
For more information on the chemistry and physics of metals, see:
For a deeper understanding of how metal use shapes the modern world please see these reports from the United Nations Environment Program, International Resource Panel, (a body that is similar to the IPCC but deals with resource use):