I acquired an Atlas 12 x 36" metal lathe years before I got hooked on woodturning.

For doing small parts of aluminum, brass, and yes, even steel, you could use your wood lathe along with an x-y slide and a tool post and a tool post holder. It won't be as rigid as a real metal lathe but there are things that you can do with it. My preference for the tool post holder is a quick change AXA (style) holder. Don't spend the big bucks on the name brand tool post holders. For what you are doing the knock offs will do fine. BTW, you may also want to get a metal turning chuck, especially for small diameter pieces.

On most x-y tables, there are gib screws to take up some of the slop. They typically arrive pretty loose. One thing that you'll learn when machining is your xy table handles/wheels will have a little backlash So, if you advance the tool by, say, 0.020" and then back it up by, say, 0.005, it is likely that the tool won't move. So all good machinists will back it off by a much larger amount and then take up the back lash and re-advance it by some lesser amount, say, 0.015.

One thing that you'll probably tire doing is advancing and backing up the cutting from right to left. The xy table will give you a fine rate of feed and you are likely to be turning that handle a lot. On my Atlas lathe the lateral manual feed is more coarse.

BTW, using my G0766, I removed about 3/8" of cast iron from the original tool post so that it would sit lower. I used a carbide cutter on the end of a 1/2" square steel bar, had minimal overhang, put a collar on the tool to limit the "feed" and took light cuts. I was doing a scraping cut. It worked fine but it was scary with the 14" wide tool post spinning just an inch from my hand.

If you are interested in turning aluminum, just give it a try using regular tools (and light cuts). You may be surprised how easy it is (even without the xy table).