Hot melt adhesives are generally 100% solids formulations based on thermoplastic polymers. They are solid at room temperature and are activated upon heating above their softening point, at which stage they are liquid, and hence can be processed. After application, they retain the ability to wet the substrate until they solidify. Upon solidification, they return to a physical state that has structural integrity and can function as an adhesive. The adhesive is applied by extruding, rolling, or spraying and joining is carried out immediately after application or after reheating the solidified layer. The variety of polymers in this class is very wide and includes both natural and synthetic polymers. The high viscosity of the melt makes them particularly suitable for porous and permeable substrates which otherwise would be more difficul to bond with a solvent system. A feature of hot melts is that on cooling they very rapidly build up their internal strength allowing rapid assembly and further processing. Because they are based on thermoplastic polymers, hot melts can be repeatedly heated to melt and cooled to solidify. This property limits the temperature resistance of hot melt bonds and they also have a tendency to creep when subjected to continuous stress or elevated temperatures. On the plus side, these adhesives can be used to create bonded joints that are thermally detachable and can also be re-attached.

Hot melts are used in industry for a wide range of applications. The packaging industry (manufacturing of packaging from paper, cardboard, and corrugated board) is one of the major users. Hot melts are also used in the printing industry for bonding the spines of books, in the textile industry for bonding appliqué, and in the shoe-making industry for bonding for example shoe soles. The wood processing industry uses hot melts for veneer surrounds and edging. The automotive industry employs hot melts for a host of applications including bonding insulating and cushioning materials, bonding headlight covers into metal frames and for wheel covers. The electronics industry also uses hot melts, for example for bonding coil windings and coil ends.