Why were nobles important to Feudalism?

Answer 1

The nobility controlled the land, and they were responsible for raising and maintaining an army should they be called upon to do so. The lords of the manor were responsible for all those under their charge.

Answer 2

The nobles were the landownersi think, they also owned the people who lived on it, they were known as serfs and were little more than slaves, and were made to swear/promise allegiance to the Lord of the land, and in the event of trouble,argueing fight and die for him as well.