Link. Four categories are used - alumium (mainly the front crumple zone), low-strength steel (mounted to the safety cell, also forms the fenders), high strength steel (part of the front crumple zone, also the battery pack) and ultra-high strength steel (passenger safety cell and its connection to the rest of the body). Body panels are not shown, but are believed to be alumium. Everything but the ultra-high-strength steel is repairable; the latter may only have things welded to it. You also need to use boron or tungsten carbide drill bits to drill through it.