If you encounter issues while trying to use MetaMask on Brave (such as an error saying MetaMask is not installed, even though it is), you need to disable Brave's wallet as the default. MetaMask does not work correctly if other browser extension-based wallets are installed and active.
- Click on the hamburger (three horizontal lines) icon in the upper right hand corner and choose the "Settings" menu:
- Using the menu on the left-hand side, choose the "Wallet" section of Settings
- Change "Default cryptocurrency wallet" to "None"
- Restart Brave.