What is the function of the Tungsten filament in a light bulb?

Because it has a very very high melting temperature: 6191F, 3422C. However it is also

very difficult to work with, so early light bulbs used carbon for making the filament instead.

Around the year 1900, carbon filaments were replaced with tantalum filaments. It was not

until about 1910 that it became practical to make tungsten filaments.