  We study light meson properties in a magnetic field, focusing on a charged
pion and a charged and polarized rho meson, in quenched lattice QCD. The
gauge-invariant density-density correlators are calculated to investigate the
deformation caused by the magnetic field. We find that these mesons acquire
elongated shapes along the magnetic field. The magnitude of the deformation is
about 10-20 % when the strength of the magnetic field is of the order of the
squared unphysical pion mass.
