What does it mean to say the Sun and Moon “rule over the day and over the night” (Gen 1:18)?

This does not suggest the author indulged in a pagan sort of personalization of these objects, or that he was tipping his hat toward Egyptian and other mythology. Of course the author of Genesis 1 did not mean to avow Sun and Moon gods (which, again, is perhaps one reason they were not named as such). The language of Genesis is poetic, though not poetry. Doubtless, the pagan traditions ultimately suggested the metaphor of the Sun “ruling” the day, just in the sense that it was the most prominent universal presence in daytime; but this hardly meant that the author of Genesis 1 took the metaphor to be understood literal. That language even as early in the Bible as this first chapter could be metaphorical is obvious. This is said to be “divided” by God from that; there are six “days” which are probably metaphorical; Sun and Moon are “great lights”; animals are enjoined to be “fruitful”; man is said to have “dominion,” as if royalty; etc.