If you want people to hear you, using metaphor in public speaking is the answer.
Metaphor are sometimes limited geographically. Metaphor can be a way to make complex ideas easy to explain.
There are some things you need to know about metaphor use.
Using Metaphor in Public Speaking Example
The term Carbon Footprint refers to "the total set of greenhouse gases (also referred to as GHG) emissions caused by a person, a business, an organization, event or product."
Sometimes, to simplify the scientific term, it will be expressed in terms of the quantity of carbon dioxide or its equivalent of other GHGs that are emitted.
Either way, to speak of either of these scientific terms will take needless time, add useless verbiage and make the speech more confusing.
Simply saying Carbon Footprint most people in the US in an audience where the term would be used will have a basic understanding of the above scientific term.
The American Dream, a home of your own, two cars, two kids, a cat or dog, 2.5 gold fish (kids of course are optional) and to be able to buy stuff is readily understood in most North American Audiences. For some, the American Dream has turned into a Personal Financial Nightmare with the lost jobs and foreclosures.
Speaking of Metaphors
Here are some more metaphor examples from the past. Start looking for current metaphors.
If you are using metaphors in public speaking, remember that as fast as they become popular, they will go out of style. Unless your creating a new one, make sure they are current.
Also, when using metaphors, remember that they are sometimes local. Sometimes they are understood by a limited number of people.