Gallium is arguably the most interesting element on the periodic table. It is a metal with remarkable properties: a melting point below body temperature, water-like viscosity, low-toxicity, reactivity, and effectively zero vapor pressure (it does not evaporate). It also has, by far, the largest interfacial tension of any liquid near room temperature. Normally small volumes of liquids with large tension form spherical or hemi-spherical structures to minimize surface energy. Yet, a thin, oxide skin that forms rapidly on its surface allows this liquid metal to be patterned into non-spherical shapes (cones, wires) in a way that is useful for soft and stretchable electronics. Liquid metals have behaviors that should be of great interest for chemical engineers: (1) In terms of thermodynamics, they have unique phase behavior such as supercooling and effectively zero vapor pressure. (2) In terms of transport, they have unique yield-stress rheology and can be used to create – for the first time –stretchable vapor barriers that overcome the long-standing trade-off between stretchability and gas permeability in polymeric membranes. 3) In terms of reactions, in addition to surface oxidation, gallium can initiate polymerization and catalyze reactions, including CO2 reduction. Perhaps the most fascinating aspect of liquid metals it the ability to use interfacial electrochemistry chemistry to remove / deposit the oxide to manipulate the surface tension of the metal over unprecedented ranges (from the largest tension of any known liquid to near zero!). We have used this principle to convert a droplet of liquid into fluidic fibers the size of a human hair or coerce liquid metal into fractal shapes. This talk will discuss these remarkable properties and highlight emerging applications that harness liquid metal.