They're high levels because Metang was caught from the wild (Giant Chasm, Bulbapedia confirms it), and the Munchlax was traded within the game.
I have the Black version. However I'm having trouble breeding them to a lower level, so you are probably better off asking Ezio-X to help you.
I have the Black version. However I'm having trouble breeding them to a lower level, so you are probably better off asking Ezio-X to help you.