Natural Gas is formed when layers or burried plants, gases and dead animals are exposed to intense heat and pressure over thousands or years. The energy that the plants  had origionally taken from sunlight is stored in the form of chemical bonds in natural gas. Natural Gas is a hydrocarbon gas (a gas made up of hydrogen atoms and carbon atoms) mainy made up by methane gas.but commonly includes other alkenes. They can also include a small percentage of carbon dioxide, nitrogen and hydrogen sulfide.