What is Metal and non-metal?

A metal is an element that, as a pure substance, is shiny when freshly cut, conducts electricity and heat well, can be bent or hammered into shape, and forms positive ions. A non-metal lacks these properties: many are gases (oxygen, nitrogen, chlorine), the solid ones are dull and brittle (sulfur, carbon as coal), and they tend to form negative ions or to share electrons in molecules.