Metals are a category of materials that conduct heat and electricity well. When they are smooth and polished, they often have high reflectivity. Metals are found in nature and refined (melted) and shaped in various ways as either liquids or solids. A metal is a material (an element, compound, or alloy) that is typically hard, opaque, shiny, and has good electrical and thermal conductivity. Metals are generally malleable as well as fusible (able to be fused or melted) and ductile (able to be drawn out into a thin wire). About 91 of the 118 elements in the periodic table are metals. Below is a list of metals commonly encountered and their density.