What makes metals malleable and ductile?
The metals are malleable because they don't make molecules : they exist as individual atoms. In a metallic piece, the atoms are identical, and they are piled up like layers of beads in the bottom of a flat box, each bead touching its neighbors. The first layer of beads covers the entire surface of the surface. You may imagine a second layer identical to the first one covering it, then a third layer, and so on. Hopefully you see that is not very difficult to push a whole layer, or a whole pile of such layers from the side. A whole layer can slide easily on a lower layer. This would not break the whole piece, which gets distorted but not broken. It would be much more difficult to do it if suddenly one or some of these beads are replaced in a given layer by bigger beads or by non-spherical objects. ${}{}{}{}{}$