  We report the synthesis of Ca$_2$RuO$_4$ thin films on NdCaAlO$_{4}$ (110),
LaAlO$_3$ (100) and LaSrAlO$_4$ (001) substrates and show that epitaxial strain
induces a transition from the Mott-insulating phase of bulk Ca$_2$RuO$_4$ into
a metallic phase. Magnetometry and spin-polarized neutron reflectometry reveal
a low-temperature, small-moment ferromagnetic state in metallic Ca$_2$RuO$_4$
films.
