If your butterflies have a detachable body, gently bend the metal tabs and remove the body.
Spray paint the undersides to give them a finished look. Let dry.
Lay the butterfly and any body pieces on the paper of choice, and trace around them with a sharp pencil.
Cut out the paper into separate pieces.
Coat the back of the paper with decoupage medium, and apply the paper to the butterflies.
Smooth the paper out with your fingers or a brayer. Let dry and then top coat with Mod Podge.
Once dry, you can snip the edges with scissors if there is any paper overhang. An emery board can also be used if you want very smooth edges.
Re-attach the body to the wings, then flip over and glue a magnet to the underside using E-6000. Let dry.