Face Electron

Face Electron
How does copper’s structure help it?

How does a face-centred cubic lattice contribute to it’s excellent conductivity and malleability? (apart from the ‘sea of electrons’ metallic bonding, because copper stands out for some reason)

see this reference. It is exactly what you are looking for for the malleability bit.

basically the FCC lattice has the most slip planes available of any lattice for the non destructive re-arrangement of the lattice during a deformation event.

as for the electrical conductivity the FCC lattice is the most compact or dense lattice type and thus for a metal provides more electrons per unit volume to the free electron cloud than any other lattice type for a given type of metal atom and more electrons means more charge carriers for conducting electricity.

for thermal conductivity, in a metal this approximately tracks electrical conductivity according to the Wiedemann-Franz law so the same theory applies.

Also it should be noted that the conductivity in an FCC lattice is equal in each of the three lattice axes due to the symmetry. This is not the case for other lattice types and so conductivities in these materials can be highly anisotropic.