Tracey here are the beliefs from what the ancients knew, there are also a connection with the seven chakras and seven days etc.... Seven planets was all they knew!
In ancient Greek mythology, each of the seven known bodies spinning around the Earth were associated with a different metal:
Sun – Gold
Moon – Silver
Mercury – Mercury
Venus – Copper
Mars – Iron
Jupiter – Tin
Saturn – Lead
The ancients mythologized that as the planets spun around the Earth, they each spun their individual metals (influences) into the depths of the Earth.
Here's a short quote from Jungian author Edward F. Edinger:
"Psychologically we can understand this image as referring to the archetypal constituents of the ego. The building blocks of ego are divine qualities stolen from the gods or products of dismemberment of a deity – earthly representatives of transpersonal principles."
Applied astro-psychologically – we understand the imago myth of the planets revolving around the Earth to refer to the human ego's stance (our sense of "I") in life. Based on this image our individual life journeys place each one of us (subjectively speaking) in the center of the universal, archetypal energies of the planets spinning 'round us.... and each one of us is then cast in the starring role of our special life journey.