If it was me Chris, I wouldn't worry about "the boy" (hasn't the poor chap got a name?) preferring metal over wood. It sounds like he got the "hand work" bug in him (personally I don't like the "Maker" label, but that's just me) and the main thing is that you continue to help and encourage him.
Most likely he'll find out for himself that some things are better made in metal, others in wood (speaking very generally) and he'll "move back and forth" now and again, as and when he sees the different needs.
And you could also think about "moving over" a bit yourself too!
Without wishing to repeat myself, I hope you get a copy of that book I listed before, about making wood work devices by Robert Wearing. I only came across it myself quite recently, and was surprised to see how much of a wood/metal mixture there is in there - AND there's the bonus of making some things which you can both put to good use in "the wood working department".
And again, sorry to repeat, but that Stan Bray book I listed before is also well worth it - like the Wearing book it's got a lot of little gizmos he can make for future use in his metal working, AND it gives a very good overview of the whole subject, touching (albeit briefly) on just about every "branch" that's already been mentioned here in this thread. It sounds like his school is doing a good job of introducing him to the whole arena, but further background reading can't be bad.
Good luck and "more power to yer elbow "boy""! It's really great to hear of a young chap getting interested in "the old skills"!