It doesn't sound good, does it ?
It's very difficult to judge without knowing when the oil was last changed but a motor which is run-in and oil-changed at the correct intervals wouldn't normally have anything more than a fine grey metallic smear with perhaps the odd shiny flake in.
If the material is definitely magnetic, I would fear for camshaft problems, they produce vast amounts of material once they start to go.
I suspect that unless you feel ready for a pre-emptive strip-down, the best advice is to clean the oil tank thoroughly, replace filter if it has one and wipe out the inside of the cases as best you can via the sump strainer opening.
Perhaps than refill with clean oil and run for 100 miles or so to see what is picked up. If it seems to be reducing and you have no other symptoms of imminent destruction then give it another change and treat it as normal after that.
Sadly, I think that many of us have become unwilling experts in self-delusion when the drain plug starts to resemble a small pine cone. Fearing the worst is usually the right thing to do
