Question

what atomic-level feature gives metals their strength?
tightly packed atoms in a regular structure
electrons that float between atoms
energy from the battery
sharp edges in the atom

Explanation:

Metals have a metallic bond. In this bond, electrons are delocalized (float between atoms). The electrostatic attraction between the positive metal ions and these delocalized electrons gives metals their strength. Tightly - packed atoms in a regular structure (like in some crystals) can contribute to hardness but not the characteristic strength of metals. Energy from a battery is not related to the atomic - level feature of metal strength. Atoms do not have sharp edges in the context of giving metals strength.

Answer:

Electrons that float between atoms