There are only two ways of energy transfer; one as result of temperature difference and other where temperature difference is not involved. In the later we may be able to visualize it as work done by some force or we may not be able to do so. But with our pre-decided conception of energy we find that energy of one object gets reduced and the other gets increased then we say that the object or system whose energy is reduced has done work upon the object which has gained energy. The concept of energy is related to work on one hand and force on the other.
