Metaknight is a stacked character... He has a surprisingly good array of short powerful attacks. You can improve his range game with practicing certain moves like his arial A's. If you go into training mode and set the speed low, you can study his movements and understand the range of his attacks better. I know training mode sounds old fashioned, but being able to create certain environments can be key to fully understanding the depth of a character. Anyways, it really comes down to the player and their understanding of how to use this character. His "peak point of range" is around 3/4 the total range of marth if hit at the perfect dircetion, distance, etc....
Of course, you can always take marth into training mode and do the same thing. I usually never go into training mode unless I am really in the need to understand the moveset animations. Hope this helps...