Metal nanowires, such as silver nanowires coated on a substrate were sintered together to form fused metal nanowire networks that have greatly improved conductivity while maintaining good transparency and low haze. The method of forming such a fused metal nanowire networks are disclosed that involves exposure of metal nanowires to various fusing agents on a short timescale. The resulting sintered network can have a core-shell structure in which metal halide forms the shell. Additionally, effective methods are described for forming patterned structure with areas of sintered metal nanowire network with high conductivity and areas of un-sintered metal nanowires with low conductivity. The corresponding patterned films are also described. When formed into a film, materials comprising the metal nanowire network demonstrate low sheet resistance while maintaining desirably high levels of optical transparency with low haze, making them suitable for transparent electrode, touch sensors, and other electronic/optical device formation.