A conceptual or common metaphor is one that we use with little notice. In fact, some metaphor is so pervasive that we must struggle to avoid falling prey to its subtle suggestion. Consider ...
LakoffAndJohnson's MetaphorsWeLiveBy, and also GeorgeLakoff's WomenFireAndDangerousThings, introduce the theory, philosophy and politics of conceptual metaphor. Or, perhaps even better, Janet Martin Soskice's "Metaphor And Religious Language" (ISBN 0198249829 ).