I grew hyacinth bean in a metal container with attached
pyramidal tuteur one year, intending to twine the
bean vine up and around it to the top. Well, it never lived that long. The poor thing fried in the can. Now I line the container, sides and bottom, with 2 layers of coco-fiber mat, and plant ivy in it instead, which will take partial shade.

You might want to try using the coco-fiber as an insulator around the outside of the formula cans, tying it up near the top with some string or raffia, which might be pretty.

Or, use the cans for late winter seed starters for heat lovers like tomatoes and peppers. They might appreciate the extra warmth and grow faster to transplant size. Even so, I wouldn't leave the cans out in strong sunlight all day.