The sun converts 4.3 million tons (4.3E+09 kilograms) of mass into energy every second ... equivalent to the mass of 1 million elephants. It has been doing this for the past 4.6 billion years.
This is not to say that the sun is made of jelly beans or elephants. The sun fuses hydrogen into helium with part of the hydrogen's mass being converted into energy. A little mass produces an enormous amount of energy.