I'm not a tax professional, although I do study the stuff. (Paging @cryptotax) My layman's impression is that there's not necessarily a category of "commodity" in the tax code--there's just property, with subcategories of collectables and the like. Capital gains still apply, just with different taxes. Of course, I'm not speaking with authority, here.

Here's an article by someone who actually knows what he's talking about: https://www.forbes.com/sites/baldwin/2017/06/13/how-are-commodities-and-commodity-funds-taxed/