Glass, porcelain, plastic and rubber are examples of non-conductive materials. These materials are also known as insulators. They are used to stop the flow of electricity.
Insulators either prevent or block the flow of electrons. The atoms inside insulators do not have extra electrons that can move freely through a material. However, there is no such thing as a perfect insulator since an insulator can become electrically conductive.
The opposite of insulators are conductors. Examples of conductors include copper, aluminum, platinum, gold, silver, ionized water and trees. Conductive materials are compounds that are comprised of atoms with free electrons. These electrons are able to move freely through the conductive material and allow electricity to flow.