Copper has an electron structure of $\ce{[Ar] 3d^10 4s^1}$. In salts it may form two stable ions, the $\ce{Cu^+}$ and $\ce{Cu^2+}$. (It's actually not very clear to me why the 2+ ion is common, why does it readily lose one of its d orbital electrons, but I'm willing to wave my hands and say "something quantum").
In pure copper metal, in the usual high school picture of metallic bonding, the conduction band electrons delocalise leaving a structure with ions "floating in a sea of delocalised elections". In copper, how many of its electrons delocalise? Does it make sense to describe copper metal as $\ce{Cu^+}$ or $\ce{Cu^2+}$ ions surrounded by an electron ocean?
Image of metallic bonding from BBC bitesize
The linked page says that in group 2 metals, both valence electrons are delocalised, but I've also read that in copper, the whole $\ce{3d^10 4s^1}$ electrons are all valence electrons.