Existing strategies for 3D printing of metals tend to be expensive, energy-intensive, and usually require high temperatures (for sintering metal powders) or low pressures (to avoid oxidation). These procedures are incompatible with polymers, organics, soft materials, and biological materials. We present an alternative system that utilizes low melting point alloys based on gallium as complements to the current materials for 3D printing applications. Despite having high surface tension and low viscosity, these metals form mechanically stable structures due to the formation of a thin (~3 nm thick) surface oxide. The oxide is passivating and forms rapidly and spontaneously on the surface of the metal. We utilize this property to print free-standing 3D liquid metal microstructures such as wires, fibers, interconnects, and stacked arrays of droplets at room temperature on soft surfaces using low dispensing pressures (~10s of kPa). The smallest components fabricated are ~10 Ám wide. These alloys are easy to print and offer the electrical and thermal benefits of metals. The ability to direct-print metals on flexible polymers at room-temperature is important for fabrication of soft, stretchable and flexible analogs to conventional rigid wires, electrical interconnects, electrodes, antennas, meta-materials and optical materials.