Here's why:

* Stars are giant balls of hot, glowing gas. The Sun is primarily composed of hydrogen and helium, which are in a plasma state due to the intense heat and pressure.

* Gas planets, like Jupiter and Saturn, are mostly made up of gases (hydrogen and helium) but have a solid core.

* Rocky planets, like Earth and Mars, have solid surfaces composed of rock and metal.

So, while the Sun is made of gas, it's not a planet. It's a star, a massive ball of hot gas that generates its own light and heat through nuclear fusion.