Abstract: A method and apparatus for forming a seam on a thermoplastic coated container, which container has been formed from a single blank or a continuous by bending the substrate member from which container was formed and overlapping opposite edges thereof to form the seam. According to the practice of this invention, the edges of the substrate member which are to be overlapped and joined to form the seam are each heated, prior to their overlapping, by energy from a laser to thereby render the thermoplastic coatings on the overlapped portions of the substrate member soft and tacky so that they will adhere to each other when pressed together and allowed to cool. The laser energy is applied by directing an unfocused laser beam of 10.6 .mu.m wavelength over a zone about one-half inch in width to each of the two edges, the web or blanks being fed along a conveyor past the stationary laser sources.