The metal outer cover of a bee hive is commonly used as the topmost protective layer for the hive. Its main purpose is to protect the bees and their colony from the elements, such as rain, wind, and sunlight. The metal outer cover also helps to keep the hive warm in the winter by retaining heat and cool in the summer by reflecting sunlight.

Additionally, the metal outer cover is typically designed with a lip or overhang that helps to prevent water from entering the hive, and it is often fitted with ventilation holes to provide airflow and regulate the temperature inside the hive. 

Overall, the metal outer cover is a critical component of a bee hive that helps to protect the bees and their colony from the elements, regulate temperature, and provide ventilation for the bees.