Droplet sizes produced inGMAW are predicted using both thestatic force balance theory and the pinchinstability theory as a function of welding current, and the results are comparedwith experimental measurements. Thecauses for the deviation of predicteddroplet size from measured size are discussed with suggestions for modificationof the theories in order to more accurately model metal transfer in GMAW.The mechanism of repelled metal transfer is also discussed. The transition ofmetal transfer mode has been consideredas a critical phenomenon which changesdramatically over a narrow range ofwelding current. This transition has beeninvestigated experimentally using highspeed videography which shows that thetransition is much more gradual than isgenerally believed. The mechanism ofthe transition is discussed using a modified static force balance theory.