How to use Cardano's metadata feature?

To use Cardano's metadata feature:

1. Decide on the data you want to include as metadata (must be 16KB or less).
2. Structure your metadata according to the CIP-10 standard, typically in JSON format.
3. If using a GUI wallet, check if it supports metadata attachment (some may not).
4. For advanced users, use the Cardano CLI to create a transaction with metadata.
5. Prepare your transaction as normal, then add the --metadata-json-file parameter with your metadata file.
6. Submit the transaction to the network.
7. Once confirmed, your metadata will be permanently recorded on the blockchain, retrievable using the transaction ID.

Metadata can be used for various purposes like timestamping documents, adding notes to transactions, or supporting off-chain protocols.