You’ll need to configure the Matic Network custom RPC to your MetaMask. It’s pretty simple and straightforward, and it’s easy to switch back and forth between Layer 1 and Layer 2 using the button near the top of the MetaMask application.
Click on the network selection button on the top of the app.
Click on the “Custom RPC” to add the Matic mainnet information.
Select “Custom RPC”.
After clicking “Custom RPC”, a screen will appear allowing you to set up the custom RPC for Matic Network. Enter in the Matic mainnet details as follows:
Network Name: Matic Mainnet
New RPC URL: Select one of the following
Chain ID: 137
Block Explorer URL: https://polygonscan.com/
Once you’ve added the details click on the “Save” button. You’ll then be connected to the Matic mainnet. That's all!
Lastly, if you need a bit of MATIC coin to pay for gas fees for your first transaction, please visit the Polygon faucet at http://matic.supply