A light bulb is a ball of glass. Most of the air inside a light bulb has been removed. The base can be screwed into a metal socket, which is a good conductor. Electricity flows through a conductor, but not through a(n) insulator. Current flows through a thin wire called a(n) filament. The filament is not a good conductor. It is a resistor. Current does not flow easily though a(n) resistor. This resistance absorbs some of the current, causing the filament to get so hot it glows. This is how the bulb creates heat and light.