I use rare earth magnets about .5" dia. around my
oil filters. I just stick 4 of them on opposing sides near the bottom. No fear of falling off as these are very strong. I cut a can open 1 time and there were dark rings around where the magnets were; so they are doing their job.
I got the idea from a product I found for small airplanes that strapped around the filter can. It had to be 4 and positioning was important as the poles interacting enhanced the metal-attracting properties of the magnets.