Then again, I've seen it repeated (though would appreciate someone backing it up with a citation) that on planetary scales, everything behaves like a high-viscosity liquid. That was in context of modeling e.g. moons hitting planets.
It seems to be, yes. [0] cites IAU definition, which mentions "hydrostatic equilibrium", suggesting at this level things are viewed through the lens of fluid mechanics.
From xkcd:
> On that scale, the polymers in the bowling ball would behave more like a liquid
So polymers, not metal.