Post History
I wrote this before the poster indicated that this was a speech. My advice still applies, it just needs to be on a shorter timeline. Write what you want, show it to people you trust, revise, then...
Answer
#4: Attribution notice removed
Source: https://writers.stackexchange.com/a/45419 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/45419 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
I wrote this before the poster indicated that this was a speech. My advice still applies, it just needs to be on a shorter timeline. Write what you want, show it to people you trust, revise, then show (or read) it to a more diverse group of listeners, especially those similar to your expected audience. * * * I'd say your question applies to every word you commit to paper. Nothing's special about metaphors. Like what do people from different walks of life think about the fact that a story has unmarried people living together romantically? What do they think about setting the story in Baja California, Mexico vs the south of France? What about slang words in the dialogue? Or accents. Or a million other things. I don't think there's any answer aside from "ask them." This is true for any metaphor but also for other things. Your best bet is to write what you want, how you want it, then show it to trusted people as you go. See what lands wrong. Then, when it's done, get beta readers and make sure you get a variety of ages, if age is your main concern. Metaphors are easy to change, if you find that one is confusing your readers. Unlike changing a setting or character setup. And if the particular metaphor happens to be important to the plot or theme, then you'll explain it throughly in the text. See what your pre-publication readers have to say. If they flag things, send those out to other people for comment. If you don't have friends that aren't your age, ask them to ask their kids and grandkids. But don't worry about people not getting certain things, as long as they aren't central to your story. Young people tend to assume anything that an older person says that they don't understand is just due to old age and they politely let it pass (then make fun of it on social media, but that's besides the point). A few odd sayings won't turn off readers. They'll care more about your story and how you tell it.