How to attach sheet metal to wood permently without nails?

Maybe appoxy,I have seen all kinds of sealants in local Walmart,that cover’s pretty much everything including wood. Please know it is a suggestion.

PLIOBOND rubber cement.

My go to adhesive is Power Grab. I use it at Habitat homes to install backsplash tiles. It holds well, and sets up quickly. You will find it in paint section of home improvement stores. It normally comes in a caulking tube, but I think you can get it in a squeeze tube too. I would weight the sign for a short time after adding the Power Grab. You don't need too much - keep away from cut outs so it doesn't get exposed.

Indoor outdoor,bonds anything https://www.homedepot.com/p/GE-Silicone-Iron-Grip-10-1-oz-Clear-Silicone-Adhesive-HD90058/206692092?cm_mmc=Shopping%7CG%7CVF%7CD24%7CGE%7CNA%7CPLA%7CGE_Sundries_Paint%7c71700000034484723%7c58700003962211936%7c92700037225265325&gclid=EAIaIQobChMIh5-szKnh3gIVBh6tBh1Fnwz8EAQYASABEgLGePD_BwE&gclsrc=aw.ds

Loctite Superglue