A method of attaching a thermoplastic-based workpiece and a metal workpiece involves the use of a metal reaction coating. The metal reaction coating is applied over a base metal substrate of the metal workpiece such that the metal reaction coating faces and contacts the thermoplastic-based workpiece when the two workpieces are assembled in overlapping fashion. To attach the workpieces at their faying interface, an energy source such as, for example, a laser beam or an electric arc, is directed against the metal workpiece to create a zone of concentrated heat that at least warms up the metal reaction coating and melts a portion of the thermoplastic-based workpiece. Such heated activity at the faying interface promotes interfacial chemical bonding between the thermoplastic-based workpiece and the metal workpiece that contributes to an enhanced attachment between the workpieces.