No, MetaTrader 4 is not a broker. MetaTrader 4 is a Trading Platform (software) that can be installed on a local computer. MetaTrader 4 (MT4) is predominantly used on Windows systems, or can be used on a Mac. MT4 is also available as a mobile app on both Apple IOS or on Android.
Retry logging into your MT4 account, it's possible you made a typo on your account number (username) or password.