The viscosity and the shear relaxation behavior of supercooled Ag- and Sn- metaphosphate liquids are measured using parallel plate techniques. The fragility index m of these liquids, when taken together with that of other metaphosphate liquids, shows variation over a rather large range spanning from ~30 to 90 and is found to be a sensitive function of the strength and extent of connectivity or coupling between the phosphate chains provided by the modifier-oxygen coordination polyhedra. The high fragility of the Ag-metaphosphate liquid (m ≈ 90) is a result of the weak inter-chain coupling which is manifested in a polymer-like rheological behavior that is in contrast with the network-liquid like behavior of the metaphosphate liquids with lower fragility.