MyEtherWallet, the most popular online Ethereum wallet service, can communicate with MetaMask and exchange information directly. This means that when you visit MyEtherWallet using a browser with MetaMask, you have a single click login, assuming your MetaMask account is also locked. If you're not familiar, a Dapp is at least partly the type of application that resides on a blockchain such as Ethereum. Not all Dapps work on Ethereum. A number of projects and companies already have live Dapps that you can interact with today, or they have test Dapps that are open to public review. Dapps are in many ways similar to other websites. They can have detailed graphical interfaces and have extremely advanced and user-friendly interfaces. The only difference between a Dapp and a regular web application is that Dapps interact with a blockchain in the backend. MetaMask allows its users to use web browser based applications. MetaMask is a really useful, secure and flexible application.