Natural gas is a combustible mixture of hydrocarbon gases, primarily composed of METHANE, ethane, propane, and HELIUM. It is found in underground reservoirs and is used as a fuel for heating, cooking, and electricity generation. Ethane, with 6 letters, is a colorless, odorless, flammable gas that is the second most abundant component of natural gas. METHANE, with 7 letters, is the primary component of natural gas and is a colorless, odorless, flammable gas. HELIUM, with 6 letters, is a colorless, odorless, non-flammable gas that is the third most abundant component of natural gas. Propane, with 7 letters, is a colorless, odorless, flammable gas that is the fourth most abundant component of natural gas.