  Despite extensive investigations of dissipation and deformation processes in
micro- and nano- sized metallic samples, the mechanisms at play during
deformation of systems with ultimate, molecular size remain elusive. While
metallic nanojunctions, obtained by stretching metallic wires down to the
atomic level are a system of choice to explore atomic scale contacts, it has
not been possible up to now to extract the full equilibrium and out of
equilibrium rheological flow properties of matter at such scales. Here, by
using a quartz-tuning fork based Atomic Force Microscope (TF-AFM), we combine
electrical and rheological measurement on angstr\"om-size gold junctions to
study the non linear rheology of this model atomic system. By submitting the
junction to increasing sub-nanometric deformations we uncover a transition from
a purely elastic regime to a plastic, and eventually to a viscous-like
fluidized regime, akin to the rheology of soft yielding materials, though
orders of magnitude difference in length scale. The fluidized state furthermore
highlights capillary attraction, as expected for liquid capillary bridges. This
shear fluidization cannot be captured by classical models of friction between
atomic planes, pointing to unexpected dissipative behavior of defect-free
metallic junctions at the ultimate scales. Atomic rheology is therefore a
powerful tool to probe the structural reorganization of atomic contacts.
