In any chemical reaction some bonds are broken (in the reactants) and new bonds are made (to form the products). Bond breaking requires energy. Bond making gives out energy. Chemical potential energy is ultimately a result of the fact that some bonds are more stable (have a higher bond enthalpy) than other bonds. If more energy is given out when new chemical bonds form than is required to break the bonds in the first place- overall the reaction is exothermic. Overall, energy will be given out.
So generally speaking, any substance that is able to react to form substances with more stable bonds (overall) will give out energy in the process. Such a substance is therefore said to have chemical potential energy.
Example: Methane reacts with oxygen to form carbondioxide and water. This is a combustion reaction. The bond enthalpy of carbondioxide is very high (i.e. it has very stable bonds) hence the reaction is exothermic- heat energy is given out in the reaction. In fact many reactions that produce carbon dioxide are exothermic due to carbondioxide high bond enthalpy *(there are exceptions too!)