"Why" is a valid question until and only until you get to the edge of knowledge. At that point it's "physical laws".

For example, "Why is the sky blue?" is a valid question and has answers.

"Even seemingly impossible questions like, "Why is there magnetism." can be answered by applying special relativity to electric fields. (Feynman answered this question poorly in the Horizon interview which might be where you got the idea that why is a bad question.)

You end up at, "Why are there photons?" which can't be answered. (Or maybe can't be answered yet.)

My interpretation of the question was why so many elements in the periodic table are metal and that does have an answer. It relates to the number of electrons on the outer shell that are mobile because the more electrons in an atom, the "farther" away they are and therefore are mobile. That electron mobility gives the element properties that we call "metal".