The Viking Age lasted from about 793 to 1066 AD, and it had a big impact on the early development of what we now know as Sweden. During this time, Vikings explored new lands, traded goods, and settled in various regions. Their activities helped to create a united Swedish state.

1. Trade Networks: Vikings created wide trade routes that connected Scandinavia to Europe, the Middle East, and Asia. Some important trade items included:

• Silver, especially from Arab countries. In fact, about $10,000 worth of silver coins was discovered in Sweden.
• Furs and timber, which were really important for Sweden's economy.
• Weapons and handmade goods, which improved local skills and helped towns grow.

2. Cultural Integration: The Vikings introduced many different cultural influences, which shaped Swedish society. Because of their interactions with others, we saw:

• The adoption of Christianity around 1000 AD, which included new religious practices and the building of churches.
• The rise of new ways of governing, moving from local leaders to a stronger centralized rule.

3. Settlements and Clans: Viking settlements helped create clans and tribal groups. Some important clans were:

• The House of Munsö, linked to early kings like Eric the Victorious.
• Efforts led by rulers like Olof Skötkonung, who ruled from 995 to 1022 AD, to unify the region.

4. Military Organization: The Vikings also contributed new military strategies that helped strengthen the young kingdom. They used gatherings called 'Things' to organize their forces and create laws.

In conclusion, the Vikings played a huge role in building the Kingdom of Sweden. Through trade, cultural mixing, settlements, and military organization, they helped lay the groundwork for a united nation that would grow in the years to come.