Metal holders are objects that are used to store and contain metals. The term 'metal holders' can refer to a variety of objects, such as buckets, containers, and ore carts. In this case, the crossword solution for the term 'metal holders' is 'ores, ' which refers to rocks or minerals that contain metal. Ores are mined from the earth and then processed to extract the metal they contain. Metal holders are essential for storing and transporting ores, as well as the metals extracted from them.