Metal joining by means of components heating to the melting temperatures was known thousands years ago in old age Greece. Heat sources have been developed from forging furnace to modern methods of plasma arc welding, electric resistance welding, oxy-fuel welding or laser welding. Laser, as a source of intensive light beam, starts to be implemented into industrial welding systems due to its advantages in comparison with classic methods, for example narrow heat affected zone, deep penetration, flexibility and many others. Besides the welding of compatible metals it is also possible to weld plastics.