I started renting several years ago and moved into this house that is what they call a Lustron it did not dawn on me the walls were metal untill i moved it they it dawned on me how was I going to hang anything  I priced huge magnets and that was out of the question. I can tell you that I have used every single size of hook and they all work in every room . If you try to be a cheap knock off that is what you will get a cheap knock off that will not hold.