MetalGreymon, affectionately nicknamed "Puffy" by his tamer, which is completely ironic because MetalGreymon is anything but kind and friendly. MetalGreymon is typically very savage indeed, and usually has a speech impediment to match that behavior. While he IS kind and gentle as Botamon and Koromon, as soon as he becomes Greymon and later stages he becomes more brutal with how he acts, often starting unnecessary fights with both enemies and friends alike. Like the other five Digimon of Tanker Town, he prefers his Ultimate form over his Mega or previous forms, as that was the form he can always maintain more than any other form. His digivolution as Virus MetalGreymon is a homage to the original Digimon V-Pet Version 1.
Botamon is the Fresh form of Puffy, and is most often seen whenever Puffy degenerates from his Mega stage, BlackWarGreymon.
After fighting Eaglemon in the beginning of the series, Puffy is degenerated down into Koromon, and stays this way until Episode 2 where he digivolves into Agumon when facing a Monochromon along with the other Digimon.
Puffy's Rookie Form, often used early on in the story before the Digimon reach Champion level. His attacks become more fierce in this form, and he is more savage than he was as a Koromon or a Botamon.
His personality becomes even more savage upon reaching this form, but his attitude towards Shout is still the same. He prefers to brawl with the enemy to weaken them first and then use Nova Flame on them when they are weakened. The reason for his digivolution into Virus MetalGreymon is due to his savage nature, hence why he also becomes BlackWarGreymon as well. Ironically, though, he doesn't digivolve into SkullGreymon at all. His digivolution to Virus MetalGreymon is also due to the fact most of the digivolution lines of the main cast Digimon are based on older media in the franchise, in this case, Virus MetalGreymon existed before Vaccine MetalGreymon.
BlackWarGreymon, rather than talking, is more likely to solve conflicts by tearing enemies in half rather than peaceful negotiations, or just flat out incinerate them with Terra Destroyer. Puffy acquires this form when he feels most at rage, where the others can digivolve to Mega more freely.