At work I was driving holes in nitrous tanks before throwing them in the recycling bin and every time I think, man I wish I had a project idea for these 1/4” wall steel containers, it seems like such a waste.
I like the aerator idea, they are kind of small being anywhere from 3 inches to 6 inch diameter tubes. Seems kind of small for fire pit thing. I’ll have to look it up.
Or you could fill them with sand and add the center shaft to run behind a lawnmower make them into lawn rollers. My neighbor has one and puts patterns in his lawn with it. No idea how heavy his is or if it would need to even be filled.