>>27107099Well, Metagross has a digestive system, which means fleshy bits. By steaming it, ideally internally, the metal will heat up and expand until the basic structure can't withstand the pressure anymore and it pops away from the flesh. The meat should be seared a bit from the process.
For Glaceon, you have to pickle the meat. Some pickling styles essentially cook meat with no heat required, thereby preventing Glaceon from becoming a slushie.