It's too simplistic, by far, but it can serve as a useful metaphor.

Finally, the useful little extended metaphor made it.

A useful metaphor for this system is a freight train.

The recognition of city rhythms is a useful metaphor, helping to understand modern city life.

This problem has a useful metaphor in the leap-year problem.

It is sort of hard to see it as a useful metaphor for golf.

"It would be a shame not to bring the trampster with me, you know-such a useful metaphor for labor in the 1990s."

It's been striking me lately as a useful metaphor.

A useful metaphor for production in an economy comes from the kitchen.

I find this a useful metaphor for much of what is happening in the world of architecture today.