Abstract: An electroless metal plating bath composition, a corresponding method for electrolessly depositing a metal onto a substrate surface, as well as the resulting, metallized substrate, are disclosed. The inventive bath composition includes water, a soluble source of the metal ions it is desired to chemically reduce at, and deposit onto, the substrate surface of interest, and a complexing agent for the metal ions. In addition, the bath composition includes a soluble source of any one or more of a select group of what are termed mediator ions, which group includes palladium (Pd), platinum (Pt), silver (Ag), ruthenium (Ru), iridium (Ir), osmium (Os) and rhodium (Rh) ions, as well as a complexing agent for the mediator ions. Moreover, the bath composition includes a chemical reducing agent, which primarily serves to chemically reduce the mediator ions at the substrate surface of interest.