Electromagnetism

Electromagnetism is a force that effects anything with an electrical charge.  Also, electrically charged objects produce an electromagnetic field.  Like gravity, an electromagnetic field weakens with distance.  Electromagnetism is the force we observe most often and explains most phenomena seen by humans (with the exception of gravity, of course).  Atomic bonding, molecular interaction, and even some particle interactions all are caused by the electromagnetic force.  This force is carried by the photon.