  Metis, the coronagraph on board Solar Orbiter, provides for the first time
coronagraphic imaging in the ultraviolet HI Ly-alpha line and, simultaneously,
in polarized visible light, thus providing a host of information on the
properties of CMEs and solar eruptions like their overall dynamics, time
evolution, mass content, and outflow propagation velocity in the expanding
corona. We analyzed in this work six CMEs observed by Metis between April and
October 2021, which are characterized by a very strong HI Ly-alpha emission. We
studied in particular the morphology, kinematics, and the temporal and radial
evolution of the emission of such events, focusing on the brightest UV
features. The kinematics of the eruptive events under consideration were
studied by determining the height-time profiles of the brightest parts on the
Metis plane of the sky. Furthermore, the 3D position in the heliosphere of the
CMEs were determined by employing co-temporal images from two other
coronagraphs: LASCO/C2 onboard SOHO, and COR2 onboard STEREO-A. Finally, the
radiometrically calibrated Metis images of the bright UV features were analyzed
to provide estimates of their volume and density. From the kinematics and
radiometric analyses, we obtained indications of the temperatures of the bright
UV cores of these events. The analysis of these strong UV-emitting features
associated with coronal mass ejections demonstrates the capabilities of the
current constellation of space coronagraphs, Metis, LASCO/C2, and COR2, in
providing a complete characterization of the structure and dynamics of eruptive
events in their propagation phase from their inception up to several solar
radii. Furthermore, we show how the unique capabilities of the Metis instrument
to observe these events in both HI Ly-alpha line and polarized VL radiation
allow plasma diagnostics on the thermal state of these events.
