Effects of organic additives on the initial stages of zinc and tin electrodeposition have been investigated at an iron electrode using a variety of techniques such as electrochemical quartz crystal microbalance, scanning probe microscopy, and electrochemical impedance spectroscopy. Organic additives were shown to play different roles depending on their functionalities. An additive such as benzoic acid acts as a leveler by specifically adsorbing on the top of dendrites, while polyethylene glycol molecules raise the overpotential for reduction of both metal ions and protons by effectively blocking the electrode surface. Throughout these studies, these in situ techniques were capable of detecting minute amounts of chemical reactions and electrical changes taking place at the electrode/electrolyte interfaces, which would have been impossible without them. These techniques were critical in elucidating the roles of the organic additives in earlier stages of electrodeposition, in which not a significant amount of reactions takes place.