Bob Owens of Bearing Arms takes a wire brush to Metcalf and his arguments in his post MORE METCALF: Dick Heads Further Left, Becomes A Useful Idiot For The Gun Control Cult.
A pertinent section: "...[D]espite a long publishing and academic career, he fundamentally doesn’t grasp the meaning and intent of the Second Amendment. Specifically, he betrayed that he either simply is incapable of understanding what the Founders meant when they stated the need for a well-regulated militia, or that he simply doesn’t agree with it. Instead of showing contrition for his ignorance (or arrogance), he continues to insist that “well-regulated” means “lawyered to death,” and that his fellow gun owners simply aren’t as good as he is."
In addition, Sebastian of Shall Not Be Questioned provides an excellent primer on the real meaning of the 2nd Amendment in Metcalf Really Needs to Stop Digging.
You can't improve on perfection - read both the above posts.