Queen Beryl was able to hold off a blast from the Silver Crystal for a short period of time, which takes a ton of power. Not to mention she destroyed the Moon Kingdom too.
I don't think Metal Sonic could stand a chance against her. The other members of the Dark Kingdom...maybe, but I doubt that he could even get past Zoisite or Kunzite for that matter.
Metal Sonic is able to scan his enemies, allowing him to adapt. Plus, who KNOWS what he could get from Beryl!
And I'm assuming Beryl would be last, so he probably copied a whole ton of abilities.
Who's to say he can't? He copied Chaos's abilities. (Turning himself into liquid metal.)