There are three main ingredients in paint: binder, solvent, and pigment. Binder is the stuff in paint that forms an adhesive so that it sticks to the wall. Unlike glue, it’s not a polymer in paint (at least not a fully formed one), but instead monomers or short polymer chains that react (crosslink) to form larger polymer networks as the solvent evaporates. The solvent in paint is there to make the paint solution the right thickness so that you can easily put it on the wall without it dripping all over the floor. Then the solvent evaporates, driving the formation of the crosslinked polymer networks. Pigments are, of course, used in paint so that not everything is painted white (though white paint still needs pigments to be white!).