How can sun burn?

Answer 1

It does NOT burn. The Sun is so hot, about 5500 Celsius at the surface and 16 million at the core that only gas and hotter states of matter can exist there.

There is no flammable material there and if you know, 98% of gas there are hydrogen and helium, so there isn't enough oxygen there for things to burn.

So how does it shine?

Deuterium and Tritium Hydrogen Atoms, those found in hydrogen bombs, merge to form helium, an energetic neutron and energy in the source of light and heat.

So many reactions take place that the sun is converting 4 billion tonnes of hydrogen into helium and vast amounts of energy every second, sending vast amounts of light, heat over the 15 billion kilometer journey from the sun right to earth.

Hope I helped.