Except… chemical bonds don’t ‘store’ energy. Molecules are a low energy configuration. It takes energy to rip them apart!
But, O2 molecules, with their double bond, don’t take much energy to break apart. If they do, and then pair up with say a bunch of Hydrogen and Carbon atoms that were nearby in some long chain or something, they form bonds that are stronger - that take more energy to break - and you end up with some leftover energy. Water and CO2 molecules are an even lower energy configuration.
but the extra energy you get wasn’t exactly ‘in’ the oxygen bond though - any more than when you have a ball at the top of a hill it has potential energy ‘in’ it.
Fusion and fission are like that but for atoms instead of molecules.