Oil, fur, silk, wool, rubber, glass, plastic, wood, paper, wax and ebonite are good insulators. Insulators are substances with tightly bound outer electrons and heavily resist the flow of electrons. Most nonmetals are classified as insulators.
Air also serves as an insulator, although when heated to very high temperatures, it becomes a conductor. Glass also becomes a conductor at high temperatures.
A conductor is a material that allows the free flow of electrons. Most metals are good conductors, as the outer electrons freely flow from one atom to another. Silver and copper are among the best conductors, but gold, aluminum, iron, steel, brass and bronze also allow electrons to flow freely.
The normal flow of electrons is random in terms of speed and direction, but it can be influenced to move through a conductive material. When electrons move in a uniform pattern through conductive material, it is called dynamic electric current. Static electricity is an unmoving accumulation of electric charge. Electrons flow through the empty spaces between atoms, similar to the flow of water through a pipe. Just as a larger pipe allows for more water to flow, a thicker strip of the same conductive material will allow more electric current to flow.