 We know that in metallic bonding the metal atoms lose their valence electrons and become ions. These ions arrange themselves into a regular lattice. The structure of the lattice is like that of an ionic solid, but all of the ions are positive. If there were nothing else there, these positive ions would repel each other and the lattice would collapse. However, the C of delocalized valence electrons occupies the space between the positive ions like glue and the electrostatic attraction between those electrons and the ions holds the lattice together. This animation from Vizchem is an illustration of a lattice of copper atoms. Notice that, like in the ionic lattice, the cations are vibrating in their fixed positions. Also like ionic substances, different metals can form lattices with different geometries. This also means that when metals are grown into crystals, they exhibit characteristic shapes. We don't often think of metals as being crystals because we usually cast them into particular shapes. But you can see with the platinum and the gold here that if left to solidify slowly, they will form obvious crystals. The lead on the right has cooled more quickly and has solidified into a blob, but even so you can see lines on the surface that correspond to the edges of crystals or crystal domains that have grown together.