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, which allows them to conduct electricity without resistance. Common examples include elements like lead and mercury. These superconductors are characterized by their simple behavior, as they transition from a normal state to a superconducting state abruptly at the critical temperature. However, they can only sustain superconductivity in low magnetic fields, making them less versatile than Type II superconductors, which can operate in higher magnetic fields.