How does metallic bonding contribute to a metals malleability?
Remember the definition of malleability: capable of being hammered out (cf. malleus , Latin for hammer!).
The property of malleability derives from the non-localized metallic bonding, " positive ions in a sea of electrons ". Each metal atom contributes several electrons to the overall structure, leaving positively charged metal nuclei in an electron sea.
The positively charged metal nuclei are free to move with respect to each other, hence the property of malleability. Another result of the delocalized electrons is that a metal can conduct electricity and heat exceedingly well. They say that gold can be hammered out to a film a few atoms thick, which I still think is quite phenomenal. But note that malleability is a property of all metals, not just the pretty ones.