Provided are methods of metallizing non-conductive substrates. The methods involve: (a) providing a non-conductive substrate having an exposed non-conductive surface; (b) forming a transition metal layer over the non-conductive surface; and (c) exposing the transition metal layer to a liquid solution of a compound chosen from one or more phosphonic acids and their salts, and monoesters of phosphoric acids and their salts, having 6 or more carbon atoms. The non-conductive substrate can be, for example, an optical fiber. Also provided are metallized non-conductive substrates and metallized optical fibers prepared by the inventive methods, as well as optoelectronic packages that include such metallized optical fibers. Particular applicability can be found in the optoelectronics industry in metallization of optical fibers and in the formation of hermetic optoelectronic device packages.