1. Angles and Saxons: These Germanic tribes migrated to Britain from what is now Germany and Denmark during the 5th and 6th centuries. They conquered and settled much of the island, bringing their language, culture, and traditions. The name "England" itself derives from the "Angles."
2. Jutes: This smaller Germanic tribe, also from the Jutland peninsula in Denmark, settled mainly in the south-east of England.
3. Norsemen (Vikings): While not as directly involved in the initial formation of the English language, the Vikings played a crucial role in shaping the language and culture. Beginning in the 8th century, they invaded and settled parts of England, introducing their language and customs. This influence is evident in many words borrowed into English, such as "skull," "knife," and "berserk."
It's important to remember that these groups weren't the only contributors to English culture and language. The Celtic people, the original inhabitants of Britain, also left their mark, as did the Romans who occupied Britain for centuries.