How do I unlock the metal category in Little Alchemy 2?

In Little Alchemy 2, the Metal category is not something you "unlock" in the traditional sense. Instead, you create the Metal element by combining specific ingredients. Here's how you can make Metal:

1. Start with Stone and Fire to create Metal.
- Stone can be made by combining Air and Lava.
- Fire is a basic element available from the start.

Alternatively, you can also create Metal by combining Ore and Fire:
- Ore is made by combining Stone and Earth.

Once you have Metal, it will be added to your collection, and you can use it to create other elements in the game. The Metal category will then be accessible in your encyclopedia as you continue to discover more elements related to it.

If you need further clarification or help with other combinations, feel free to ask!