  We quantify the scientific potential for exoplanet imaging with the
Mid-infrared E-ELT Imager and Spectrograph (METIS) foreseen as one of the
instruments of the European Extremely Large Telescope (E-ELT). We focus on two
main science cases: (1) the direct detection of known gas giant planets found
by radial velocity (RV) searches; and (2) the direct detection of small (1 - 4
R_earth) planets around the nearest stars. Under the assumptions made in our
modeling, in particular on the achievable inner working angle and sensitivity,
our analyses reveal that within a reasonable amount of observing time METIS is
able to image >20 already known, RV-detected planets in at least one filter.
Many more suitable planets with dynamically determined masses are expected to
be found in the coming years with the continuation of RV-surveys and the
results from the GAIA astrometry mission. In addition, by extrapolating the
statistics for close-in planets found by \emph{Kepler}, we expect METIS might
detect ~10 small planets with equilibrium temperatures between 200 - 500 K
around the nearest stars. This means that (1) METIS will help constrain
atmospheric models for gas giant planets by determining for a sizable sample
their luminosity, temperature and orbital inclination; and (2) METIS might be
the first instrument to image a nearby (super-)Earth-sized planet with an
equilibrium temperature near that expected to enable liquid water on a planet
surface.
