To researchers in the field, they are known as 'bad metals,' but they are not really so bad. As a matter of fact, they are the best superconductors because they are able to conduct current with the highest efficiency and without resistance up to high temperatures. This has been seen experimentally. Yet their behavior remains a mystery. The repulsive forces between the electrons in these materials are much stronger than in low-temperature superconductors: so how do particles with the same charge overcome these forces and manage to pair-up and to transport current as it happens in 'traditional' superconductors?