The metalic bond
Metals have just metal atoms. And those atoms normally want to donate electrons to form positive ions.
But: if any substance (like a metal) only has atoms wishing to donate electrons, to where can those valency electrons go? How about that?
Well, it appears that those donated (valency) electrons arrive in a kind of autonomous situation; they join, they move toghether, they stick toghether, and achieve in this way something they appreciate: space.
Besides: this is not only the case in metalic bonds, but in all chemical bonds. Electrons tend to have more space to move in
Better to say: they achieve more stability.
Those valency electrons of the metal atoms, in fact, are belonging to alle metal atoms within the substance; they all move around the atoms.
At the same time you can see it this way: They have in fact donated their valency electrons and became positive ions.