A new approach for fine tuning of the metal work function (WF) in the range of 1 eV is described. WF control is achieved by 3D molecular doping of the metal rather than the classical 2D adsorption. Both small molecules (Congo red, thionine) and polymers (Nafion, poly(vinylbenzyltrimethylammonium)chloride) were shown to affect the work function of gold and silver. The in situ reaction of the dopants within the metallic matrix is a further tool for altering the WF, confirming that this effect is dopant-dependent. We attribute this effect to the charge transfer interactions between the dopant molecule and the surrounding 3D metallic cage.