  In several two-dimensional films that exhibit a magnetic field-tuned
superconductor to insulator transition (SIT), stable metallic phases have been
observed. Building on the `dirty boson' description of the SIT, we suggest that
the metallic region is analogous to the composite Fermi liquid observed about
half-filled Landau levels of the two-dimensional electron gas. The composite
fermions here are mobile vortices attached to one flux quantum of an emergent
gauge field. The composite vortex liquid is a 2D non-Fermi liquid metal, which
we argue is stable to weak quenched disorder. We describe several experimental
consequences of the emergent composite vortex liquid.
