When you melt the metal, the impurities is denser then the actual metal itself. Sometimes it could be less dense, meaning it will float, and people scoop it off the top. Other times, filtering and draining, or just pouring and scooping the bottom off of it will get the impurities out.
Back to the question. Metal bonds, when you melt it, because the impurities get removed, meaning it is pure, and the molecules are denser and have more volume, so they like to stick with eachother. Hope this helps! :)
<span>Metallic bonds consist of the attraction of the free-floating valence electrons (negative) for the (positive) metal ions. These bonds are the force of attraction that hold metal together.A piece of pure metal, such as copper or iron, consists of metal atoms surrounded by mobile valence electrons that are free to drift from one part of the metal to another. Metallic bonds result from the attraction between the free-floating valence electrons and the positively charged metal ions.</span>
