Many users who interact with a centralized exchange like Binance eventually want to withdraw to a wallet that they fully control, like MetaMask. So once you've used their withdraw form, what could be scarier than not seeing your tokens?
We've learned that by default, Binance does not withdraw to the main Ethereum network, but instead withdraws to the Binance Chain or the Binance Smart Chain, their own blockchains, which allows Ethereum-based tokens to be held in the form of BEP2 and BEP20 respectively.
There are two ways to solve this issue, but if you've already withdrawn to any of the Binance chains, you'll have to do the longer process.
First of all, for the simplest experience with future withdraws, you can select your "Transfer Network" on Binance to be the "Ethereum (ERC20)" option, which will allow your assets to be more easily viewed on MetaMask.
However, if you already withdrew to their blockchain, you'll need to use the MetaMask add Custom Network feature to add the Binance Chain or Binance Smart Chain's RPC URLs endpoints to your MetaMask. We do not have a hosted or recommended URL for a Binance Chain node, and so you should probably refer to their documentation to find a URL they recommend.
Once you've added the Binance Chain or the Binance Smart Chain to your MetaMask, you will be able to select different networks to view the assets (you may need to add Custom Tokens too) held by your selected account on that network.
To transfer those assets from the Binance chain to the main Ethereum network, you can use their Binance Bridge site. To pay the transaction fee, you will need to buy some of their BSC token. It shouldn't take too much.
Eventually, MetaMask looks forward to making it easier for you to view assets from various networks all at once, but for now, it's good to understand where your assets are really controlled, and make your own decisions about where to withdraw them.