The sun is powered by nothing more than gravity. The weight of gas in the sun is so high it squeezes the core so hard that the hydrogen in it's core fuses together to form helium. Atoms don't like to be close together. This is why solid objects feel solid. They really aren't solid at all.
Imagine blowing up an atom of hydrogen which is composed of 1 proton and 1 electron. Most hydrogen atoms don't not have any neutrons. If you made the proton large enough to see. Perhaps the size of a sweet pea inside a football stadium the electron would be about where the "nosebleed" section is. Because of quantum physics we can't say WHERE the electron is. It's not at seat 44b say, rather the electron is spread out over all possible locations. Think of the electron as a drop of ink on a paper that somebody has smudged with their finger. The ink drop is no longer in one place but is spread out all over the page. Every thing else between this pea sized proton and the electron is empty space! The reason atoms don't pass by each other is the electrons in both repel each other very strongly. When you touch something the electrons in your hand repel the electrons in whatever you touch. so you don't really touch it. You hand is pushed away by a force field a tiny fraction of a mm away.
But if you hit something really really hard the atoms in your hand will fuse with the atoms in whatever you hit and become something else. Usually that something else is a little lighter than the sums of what your hand and the thing you hit were made of. The missing mass is converted to energy according to E=MC2 this is bad news for you because C2 is a huge number, meaning your hand will be ground zero for a nuclear explosion. Your parents might get mad at you for hitting your sister that hard so please don't hit her THAT hard. Better yet, don't hit her at all no matter how annoying she is. (The bomb dropped on Nagasaki, Japan converted 1/6 of a gram of Plutonium to produce it's huge blast. A bit of plutonium smaller than this period.)
Atoms inside the sun are squeezed together this hard, so you can see a nuclear explosion at any time of day assuming the sun is out. But it's so bright please don't look directly at it. The energy from the sun is pure nuclear energy powered by nothing more than gravity.