MetaMask

Add Polygon / MATIC to MetaMask:

Click the MetaMask icon in your browser.

Click the drop-down that says "Ethereum Mainnet".

Click "Add Network".

Enter the following information and then click Save.

Network Name: Polygon Mainnet

New RPC URL: https://polygon-rpc.com

ChainID: 137

Symbol: MATIC

Block Explorer URL: https://polygonscan.com/

(Source: https://docs.polygon.technology/docs/develop/metamask/config-polygon-on-metamask/