Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: A metallic bond is the force of attraction between a positive metal ion and the valence electrons that surround itboth its own valence electrons and those of other ions of the same metal. The ions and electrons form a lattice-like structure. Only metals, such as the copper pictured in the Figure below , form metallic bonds. Answer: metallic bond
A:
What is the force of attraction between a positive metal ion and valence electrons?