This schoolphysics webpage discusses some information regarding the heating of water using microwaves, and according to that page a common misconception that
"Microwave ovens operate at a frequency of 2.45 GHz (2.45x10^9 Hz) and this is NOT the resonant frequency of a water molecule"
But in any event the microwave energy is absorbed by the water molecules, and I assume the molecules at that point do vibrate in their various modes at their higher resonate frequencies.
But what I'm not sure of is if the polar nature of the water molecule plays any role in how the microwave energy is captured by the water molecule. I'm thinking that the microwaves being electromagnetic waves must have some influence on the water molecules that are somewhat electrically polarized by their shape.
Does the polar nature have any influence?