Type-I superconductors are materials that exhibit superconductivity at very low temperatures, typically below a critical temperature. They completely expel magnetic fields, a phenomenon known as the Meissner effect, allowing them to conduct electricity without resistance. Common examples include elements like lead and mercury. These superconductors are characterized by a single critical magnetic field, above which they lose their superconducting properties. Type-I superconductors are generally simpler in structure compared to Type-II superconductors, which can allow partial magnetic field penetration. Their applications are limited due to their low critical temperatures and magnetic field strengths.