I think that one of the most powerful metaphors brought out in the speech is the idea of the "deaf ear."  Truman had to have grasped the power of such an idea.  In suggesting that the United States not turn a "deaf ear" to the plights of Turkey and Greece, it suggests a couple of realities.  The first is that the metaphor helps to bring out the idea of the United States as the guardian of the world, not turning away its attention from those in need.  The second is that it brings out the implication that the rest of the world wishes to be liberally democratic and is under siege from a Russian threat.  The construction that Truman offers of a "world that is not static" could be seen as another important metaphor because it suggests that activity in the world is only possible with the intervention of the United States.  Truman employs the idea of stasis and change to bring out the dynamic of the need to take action, to mobilize and break through a lack of action that Truman would see as disastrous in that it would play into the hands of the Russians. In both metaphors, a clear and distinct world view is advocated.