A lot of metaphors make use of a material "objective" imagery - which is simple to understand, and just as importantly, universally understood - which is then juxtaposed with a subjective, phenomenological truth, or a relational truth that may be invisible to the senses, but which can be grasped with mental abstraction.
For various reasons, basic material objects and physical relationships - at least on the plane that concerns us, the plane of Earth - can be readily comprehended by the senses and immediately understood, which we call "simpler" than say a subjective, social, or even a technological reality, and so we reach for those understandings for leverage in explaining other truths.
There are many subjective truths, for example, that go beyond the simpler and more universal experiences that individuals have ready access to and which can be immediately recognized without much ambiguity. These deeper and more specific experiences have to be witnessed through a certain progression of events or experiences that may be more difficult to access depending on conditions and individual faculties, which can nevertheless be elucidated and made comprehensible through corresponding metaphor. And experience can be time-sensitive, requiring the stepping into of a psychic space to see the relations and truths.
This also goes for larger, more complex relations like complex societies and historical progressions. With good writing and communication, through a kind of magic, these relations can be brought into being in the perception through metaphor and illustration and exposition for the reader not previously attuned to such truths. And when brought into the perception, they can be acted on. But then the structures brought into being through language and image are nevertheless constructed, a crucial thing to remember.
