The hexagonal closest packing is used in nature to pack the largest number of identical objects into the smallest space. For example it is used by bees to construct bee hives. It also appears in crystals. In many applications it is important to have single crystals such as in the manufacture of silicon crystals for wafers used in manufacturing integrated circuit chips. Or the making of high temperature super conducting wire where the boundaries between crystals limit the ability of the wire to carry electric current.
Metals often crystallize in a three dimensional version of the hexagonal closest packed structure.
Metals that have large crystals in their structure are often strong but brittle. Metals with smaller crystals are tougher, they don't fracture, but less strong. Bend the wire back and forth a few times near the same place. Notice that the wire becomes more and more difficult to bend. It gets stronger and stronger against bending.