As a result, metals are useful as connecting wires to carry electrical signals from place to place. In fact, although it sounds odd, modern resistors are also made of conductor materials. However, they use very thin pieces of conductor which don't pass current too easily. These are materials which will refuse to carry an electric current. They are useful for jobs like coating electric wires to prevent them from 'shorting together' or giving you a shock.
Insulators are also very useful to fill the 'gap' in between the metal plates of a capacitor.
Semiconductors All the transistors, diodes, integrated circuits, etc. The basic property of a semiconductor is given away by its name - it 'conducts a little bit'. A semiconductor will carry electric current, but not as easily as a normal conductor. Some materials are intrinsic semiconductors. The semiconducting properties occur in these materials naturally.