I paint on just about anything except canvas. I don't have any canvas. My shop is a metal shop and my first choice would be copper. I love what paint does on metal. It is not absorbed, won't stay where you put it and has a will of its own. It wants to become something. When I run out of copper sheets my next choice would be stainless steel. It never rusts allowing me to put the paintings outside and it has a sheen of its own adding an element to the painting.
This time of year I like to paint on kitchen foil, what this "3"
is painted on. The depth is in the material already and I use these paintings to wrap my Christmas presents. Yeah, if you unwrap a present properly with a bit of eagerness the paint will flake off. It is still a pretty package under the tree.