An incandescent light bulb is made out of glass and metal. It is filled with an inert gas such as argon. This gas helps to slow down the deterioration of the metal filament.
Filaments are made out of tungsten, a metal prone to oxidization. To prevent oxidization, the glass bulb not only keeps in the inert gas but also keeps air out. In the early days of electric lighting, this was achieved by removing most of the air from the inside of the light bulb, forming a near vacuum inside.
Electricity runs through the filament and produces heat and light. The filaments are sometimes double-coiled out of a wire that's over 6 feet long. After coiling, the filament may be less than an inch long. Filament supports, placed below the filaments and attached to lead-in wires, keep the filaments from warping due to shock or their own weight. The filament support wires are embedded in a glass mount. Beneath the mount is a metal, screw-threaded base, which is welded to the bulb. One of the lead-in wires is welded to the interior of this base. At the bottom of this base is the base contact, which contains the other lead-in wire.