I've spoken before about the cosmic see-saw of the universe between energy and matter and I've come to a few new conclusions.
Energy is simultaneously repellant and attracted to itself. This explains and is seen in the idea of universal expansion. If given enough room, energy will space out far enough to limit as much contact with itself as possible. Like the light from a lamp, energy dissipates as quickly as possible into the lowest energy-density the volume allows. A room with no obstructions does not have an area that is brighter than any other if the light source is uniform. Like light, when there is no where for energy to go it becomes forced into contact with itself. This changes energy's properties. It creates matter. Energy that is forced to come into contact with itself overcomes its repellant properties and forms matter. Look at the skeleton of the universe and how stars and galaxies form along it. These are the areas where energy is most dense currently.
Matter attracts itself. This explains and is seen in gravity. The entire matter-based universe pulls toward itself. Or else stars would never have formed. If matter acted like energy, there would be nothing in the universe but a uniform quantity of particles resting end on end.
The more matter there is the more it tends back toward energy. If too much matter is attracted, matter forms a black hole and reverts to energy. Additionally if matter breaks down small enough it also reverts to energy. For instance, the decaying of atomic nuclei.
Matter is the form of energy trying to overcome it's own repelling tendencies when energy becomes too dense.
The cosmic see-saw between energy and matter explain the attractive and repelling forces in the universe.