Most people think that Mercury is the hottest planet because it is nearest to the Sun. However, Venus, the second nearest planet, is the hottest because it has an atmosphere. Its atmosphere is primarily composed of carbon dioxide, which acts like a greenhouse.
The solar heat enters Venus’s atmosphere, but it cannot leave, heating the planet’s surface to about 900 degrees Fahrenheit (482 degrees Celsius). This temperature is hot enough to melt several metals, including lead, tin, and zinc.