metaphor

Sometimes, metaphor and metonymy can both be at work in the same figure of speech, or one could interpret a phrase metaphorically or metonymically. For example, the phrase "lend me your ear" could be analyzed in a number of ways. We could imagine the following interpretations:
The Symbol of the Soul Form Holderlin to Yeats: A Study in Metonymy
Analyze "ear" metonymically first — "ear" means "attention" (because we use ears to pay attention to someone's speech). Now, when we hear the phrase "lending ear (attention)", we stretch the base meaning of "lend" (to let someone borrow an object) to include the "lending" of non-material things (attention), but, beyond this slight extension of the verb, no metaphor is at work.
Imagine the whole phrase literally — imagine that the speaker literally borrows the listener's ear as a physical object (and the person's head with it). Then the speaker has temporary possession of the listener's ear, so the listener has granted the speaker temporary control over what the listener hears. We then interpret the phrase "lend me your ear" metaphorically to mean that the speaker wants the listener to grant the speaker temporary control over what the listener hears.
First, analyze the verb phrase "lend me your ear" metaphorically to mean "turn your ear in my direction," since we know that literally lending a body part is nonsensical. Then, analyze the motion of ears metonymically — we associate "turning ears" with "paying attention," which is what the speaker wants the listeners to do.
It is difficult to say which of the above analyses most closely represents the way a listener interprets the expression, and it is possible that the phrase is analysed in different ways by different listeners, or even by one and the same listener at different times. Regardless, all three analyses yield the same interpretation; thus, metaphor and metonymy, though quite different in their mechanism, can work together seamlessly. For further analysis of idioms in which metaphor and metonymy work together, including an example very similar to the one given here.