Thermoplastic sealants and methods for forming a joint, such as a weld joint, between one or more structural members using thermoplastic sealants are provided. The thermoplastic sealants have melting temperatures lower than the melting temperature of at least one of the structural members. The thermoplastic sealants may further include fillers, and are disposed between faying surfaces of the structural members. The sealants can fill the spaces between the structural members to prevent the entry of chemicals, moisture, debris and other substances.