Let's say we use a very simple model consisting of non-interacting electrons in a 3D infinite square well, perhaps a cube of a single metal crystal. If an electron is in a particular energy state, then its wavefunction is spread across the entire crystal. However, electrons are said to travel through conductors like particles, implying that their position is at least somewhat localized. This would imply that an electron with a somewhat well-defined position must be in a superposition of energy states whose wave functions cancel out everywhere but near the position of the electron. So, which is it? I'm betting it's the latter one, and that the interactions between an electron and its environment act more as a measurement of its position than its energy, but I'm not sure and I'd like to hear from the experts.