> Light is purely (so far as we know) physical. It exhibits both particle and wave behavior, but neither is metaphysical.

Atheist here with university level Physics education. I want to note that qualia & subjective experience are not well explained by any current scientific model, and certainly not any model in the realms of physics.

To a non-scientist, when they say 'light is metaphysical' they may mean something along the lines of 'the experience of 'light' is not just some physical quality'.

Arguably, they might also be referring to the 'concept' of 'light', again, concepts are not well explained as objects in any physics model. Think, Plato, Theory of Forms, a perfect circle, the concept of 'pi', etc.

To try and put yourself in the religious person's shoes, imagine a philosophical zombie.

Zombie: has a brain, acts and looks just like you, says what you say, claims to think, etc. But does not actually think or feel or have any consciousness at all. Does it "experience" 'light'? Or is just cells responding to electromagnetic stimulation?

You: looks and acts the same, but experiences the feeling and emotions tied to 'light' and 'darkness' in addition to being able to quantify them in terms of physics.

It's important when arguing, to boost your opponents argument to be as strong as you can, attribute the most generous interpretation, empathize with the most creditable version of what they're trying to say (rather than what they actually do say), if you want to argue well against it and if you find a better understanding of reality.

(This 'boost other people's bad arguments, empathise with the bad arguer' process is called "Steelmanning").

lux