It allows a user to access their Ethereum wallet through a browser extension or mobile app, which can then be used to interact with decentralized applications.

[5][6] Websites or other decentralized applications are able to connect, authenticate, and/or integrate other smart contract functionality with a user's MetaMask wallet (and any other similar blockchain wallet browser extensions) via JavaScript code that allows the website to send action prompts, signature requests, or transaction requests to the user through MetaMask as an intermediary.

[11][12][13] In one instance, Google Play unintentionally removed MetaMask's official beta app before reverting the decision a week later on January 1, 2020.

[10][clarification needed] During October 2020, MetaMask Swaps, a built-in DEX aggregation service was added to the desktop extension.

[8] While MetaMask and other "Web3" focused applications claim to decentralize control over personal data and increase user privacy, critics have pointed to the default setting in MetaMask's browser extension that leaks identifiable information to data collection networks and web trackers as a fundamental privacy flaw.