The filament is usually made of steel, a material that emits light when electricity is passed through it.
It is false. The emission of light is due to the high resistance (this concept comes in higher classes) offered by the material tungsten, which has a very high melting point. Because of this property of higher melting point, tungsten is used as a filament material. On the other hand, steel has a lower melting point compared to tungsten, so it heats up rapidly, and melts insted of producing a light.