Plato and the gods

Plato's Euthyphro is a fascinating dialog about the connection between theology and morality. Of course, since the characters in it belong within a polytheistic culture, they would speak about the nature of "the gods" in the plural.
But for those of us raised in a monotheistic culture, that's an easy enough mental adjustment to make while reading it.

What is trickier is identifying the precise question at stake : Is something moral because it is what the gods command? or do they command it because it is moral?

If burying the dead in a proper ceremony is moral only because the gods command it, then are they (is He) a completely arbitrary Being, who could just as easily command one sort of act as another? Who could just as easily tell us "thou shalt kill" as "thou shalt not kill"?

After chewing that, you might move on to Plato's Republic, chapter 2. The relevant passages come near the end of that chapter, where Plato has Socrates explaining how the future guardians of the state should be educated. A proper education must not involve teaching children about the gods as Homer depicts them. (Later in the book, Plato suggests exiling poets from the Republic altogether). The Homeric gods are powerful but degenerate humans. Teaching them to children plants in children's minds the idea that it is good to get away with whatever you can in pursuit of your own pleasures.

There's some obvious synergy between these two Platonic texts and what they say about the nature of the gods Plato and his contemporaries had heard of.