Metatron’s obvious self-imposed rivalry with Castiel has always been, well, obvious, but of course as fans it was always given and taken in context as just the classic “hero/villain” rivalry. Except after “Don’t Call Me Shurley”, we get some perspective on where some of that rivalry really comes from.
No question, Metatron loves God. After feeling so abandoned, Metatron is jealous and resentful of Castiel for being “God’s fave”. Metatron’s been holding on to the fact that God chose him as his scribe like a security blanket. “There was a good reason why God left. He wouldn’t abandon me after he picked me out for something special.” And yet, absent for thousands of years, and he’s helped Castiel on multiple occasions in the span of only a few. How heartbreaking, then, for Metatron to be told that was all a lie. That his fortune was all just chance, and his father had no special love for him. Think of how the other Angels went after Metatron, thinking he was one of God’s favorites, what he endured at their hands, only for him to find out it wasn’t true. Rip that security blanket away, and Metatron has no answers.
This whole storyline was just a child trying to ask his father why he left him, culminating in the actual question: “Dad, why did you abandon me? Why was I not good enough?”
For God to help Castiel this whole time, play favorites with one son over another… Of course Metatron, loving his father the way he did, would be jealous of Castiel; see him as a rival for his father’s affections.
The Platonic solids come out of Metatron’s Cube which is centered by the “Fruit of Life” of 13 concentric circles in a hexagonal configuration, a structure that forms the foundation to the Flower of Life, the field-patterning of the quantum vacuum fluctuations of the very fabric of space-time.