In terms of non duality that is quite a plausible theory. Christianity and Hinduism teach a 'god in all' concept, though not mainstream views. The idea being that 'God' is omnipresent, omniscient and eternal. read more
“Metaphor” is a literary device, so by definition one can say “God is the universe”, or “Universe is God”, instantly creating a metaphor. But God by definition preexisted that thought I just had, so I might or might not be relating two similar things. Probably not. read more