Hybrid laser arc welding has seen renewed interest as a welding technology with the greater availability and reliability of welding lasers. Research work has been focused in two major areas: high laser powers for increased penetration and travel speed s, and the low laser power stabilization effect on the welding arc. This study examines the welding phenomena that occur with low laser power (100 to 1500 W) hybrid gas metal arc welding. Experiments were done to characterize the effects of laser power, laser spot size, laser-arc separation, and travel speed on the weld fusion zone macrostructure, arc voltage and current, and the laser and arc plasmas (imaged with high speed video perpendicular to the travel direction). It was found that increasing laser power and decreasing laser spot size increased the melting efficiency of the hybrid process over the additive melting efficiency of laser and arc welding alone. This behavior was observed at laser-arc separations of 1-3 mm and up to travel speeds of 25.4 mm/s. Increasing the laser power also reduced the current of the free burning arc but did not affect the voltage. High speed video showed the arc initiated from the point of laser incidence and was affected by both the laser power, spot size, and the potential field of the arc. These observations were consistent with the theory of thermo-field emission from the laser spot.