One of the most important aspects of copywriting is communicating complicated ideas simply.
If you want to get a feel for it you can’t beat New Scientist magazine, whose journalists are masters at doing exactly that. Anyone who can explain crazy stuff like quantum physics to a layman is worth their weight in communications gold.
Another element of great commercial writing is economy of expression.
If you want a brilliant example head for Amazon Marketplace and pick up a bunch of Nevil Shute novels. His work is best in class for clarity and elegance. It’s packed with beautiful, delicate nuances despite its simplicity. And he tells a very fine story.