B) a new element is formed
no, it not useless. we still learn Bohr's model in HS n dats almost 200 yr old! while there may be new models, previous one is good for explaining the basics. it is also useful to learn previous model n see how our understanding improves over time.
Solid metal is all different types of metals or some thing that a magnet can pick up that's a full hard solid
but a non metal is everything not metal that's a solid like plastic a hot glue gun can burn throught plastic and not metal
so in conclusion metal is stronger and thicker than non modal things