After adding a network, you will only have visibility into the number of native tokens of that blockchain network in your wallet. A blockchain can contain several tokens that have no utility for the blockchain network itself, and consequently, the amount of these tokens will not automatically appear in your wallet, even if you hold them. To address this, you should add the token’s address to your wallet and on the respective blockchain network.

You can easily find out on which network a token is available and add it to your Metamask wallet with just one click using platforms like Coingecko or CoinMarketCap.