Why is it not possible for seven close copper atoms to come together to gain a noble-gas configuration of valence electrons?

My textbook says the following about metallic bonding:



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> The metal copper has one valence electron. The valence electrons of nearby copper atoms are shared in a similar way to covalently bonded solids, but it is not possible for seven close copper atoms to come together to gain a noble-gas configuration of valence electrons as occurs in a covalent bond. Instead, the electron sharing that occurs in metals is not as restricted as in the covalent solid. 
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The problem is that this section doesn't adequately (in sufficient detail) explain *why* it is not possible for seven close copper atoms to come together to gain a noble-gas configuration of valence electrons as occurs in a covalent bond.


I would greatly appreciate it if people could please take the time to clarify this in further detail.


