The chemical synthesis of metal clusters offers a great deal of freedom in manipulating a wide range of parameters, such as the oxidation state of the metals in the cluster and the reactivity of the metals clusters due to particle-size variations, all within the bounds of the nanoscale cluster regime. Stabilization of metallic colloidal particles in polymer solutions results by the adsorption of the polymer to the metal fragments to form a film which separates the particles sufficiently to keep van der Waals forces below thermal energy levels. It has been shown that some polymers acts as good supports and sometimes ”catalysts” for the nucleation and growth of nanoscale metallic particles, with a maximal effect seen at an optimal polymer concentration and molecular weight. Among the most promising chemical avenues, is the thermal decomposition of metal carbonyl complexes in a variety of solution media, under controlled inert atmosphere, to obtain zero-valent metallic particles. Since during the decomposition reaction of metal nanoparticles highly reactive intermediate species are formed, there are two major pathways for reaction available for these species: (a) They can aggregate to form small clusters; and (b) They can attack the polymer, resulting in polymer degradation, crosslinking or metal attachment processes. The overall chemistry of a polymer-metal system will therefore be a combination of both pathways, and will be determined by the structure of the polymer used and the nature of the metallic species. Moreover, the final particle size and particle size distribution will also be a function of the various facets of this complex mechanism. In this review we will examine the mechanisms by which metal clusters are formed in a variety of solution media, and the influence of these interactions on the growth of the metallic particles and their final size.