Photons have energy and momentum. When two charged objects push or pull on each other, they send photons back and forth. So photons carry the electromagnetic force between charged objects. Photons are also known as messenger particles in physics because these particles often carry messages between objects. Photons send messages saying "come closer" or "go away" depending on the charges of the objects that are being looked at. If a force exists while time passes, then photons are being exchanged during that time.