Sun weight is about 2x10^30 kg so the Sun is more than 300 000 times massive than our Earth! Nearly all of the matter in the Sun is in the state called plasma, ionized gas containing mainly electrons and protons.

After a long long time, about 5 billion years or so the nuclear reaction burning hydrogen will cease in the core and move to the upper layers. This heats the outer layers and the Sun will slowly expand (not explode) and it becomes so called red giant. The diameter of the Sun will grow so much that it can engulf the Earth and even Mars! In the core of the Sun the helium is still burning. Eventually the helium is gone, and the core will collapse to a small white dwarf while the outer layers form a planetary nebulae.