what is ENERGY?

coal? fuel? oxygen? any matters?

NO. matter is not energy. matter is the carrier/source/container of energy.

a rock at rest only has its thermal energy.

if you threw it away, your hand put a force on the rock pushing it moving at a speed v, the moving rock will have 1/2mvv energy added on it. we call it kinetic energy. 

if the flying rock hits a wall, that energy becomes the impact force that hits the wall, makes atoms on the wall vibrate faster/hotter, atoms thermal energy. 

so, energy is nothing but vibrating force/moving force. 

energy is always vibrating/moving, within and between matters. matter is always moving/vibrating due to the existence of energy.

nothing is ever at rest, keep moving, changing, involving, reforming, transforming.

somehow, LIFE woke up?