Metaphors frequently involve the referencing of something physical. This can encourage the mind towards the physical rather than the mental. The mind is in control of the physical. The physical is in control of neither the physical or the mental.
The wise discuss the eternal.
The unwise discuss the passing.
Metaphors can be very subjective to a culture. If you wish for your wisdom to pass to and through times and cultures it is better to avoid referencing anything that is very or particularly subject to the culture you are currently in.