I found several interesting usages in today’s Wall Street Journal. I’ll post separately, to facilitate any comments. Here’s #1 of 5:

Wall Street Is Just a Metonym for Life
Alan Reynolds states, "Wall Street was always a metaphor, of course." Actually, "Wall Street," like "The Pentagon" or "Hollywood" is a metonym, not a metaphor.

Wouldn't both be right?

Not the way I understand the two words, Kalleh.

The Pentagon is a visible part of the US military, and is used to refer to the whole of it. Similarly, Hollywood and the US movie industry.

Thy face is a garden. Well, one hopes not - even with a cauliflower ear or two.

That being said, I'm not sure Wall Street is either, for life. Wall Street is a metonym for the US financial sector.

It seems to me that a metonym is an subset of a metaphor, with metaphor being the overriding concept (if that makes sense). For example, I see your point that the garden isn't the visible part of the face so it wouldn't be a metonym. And, yet, wouldn't Wall Street be a metonym or a metaphor for the US financial sector? On the other hand, perhaps I use metaphor too freely. One thing I've learned from this Board is that sometimes I use words more loosely than I should.