BlackMetalGreymon was once a peaceful Digimon. Many years ago as a BlackAgumon he sought to protecting a small village with the help of a friend. This village was home to many young Digimon who merely sought out peace and harmony. Amongst them was a BlackGabumon and even a BlackGuilmon. However, due to certain events, BlackAgumon was forced to leave and as such lost many of his friends due to these events that occurred. Ever since that day he's been on a path of anger and suffering. Once he achieved his form BlackGreymon he would kill or fight anyone who tried to get in his way. It wasn't long though before he crossed paths with Guilmon and Lance Augusta.
Lance Augusta and Guilmon fought him through teamwork and as a result, they were able to defeat him in battle but did not finish him. BlackAgumon eventually came back hunting for them and became his BlackGreymon form, desperate to defeat them as they were only the two enemies that had escaped his vicious attacks. However, Lance and Guilmon prevailed once more when they achieved Guilmon's next form, Growlmon.
BlackGreymon was defeated and as such continued to go into pure rage. He just could not accept the fact that they should be punished. He did achieve digivolution again though once his anger and rage fully consumed his mind and heart. As BlackMetalGreymon he was much faster and stronger. To this day he continues to hunt for Lance Augusta and Guilmon, to bring them down for good.