Martin Luther King, Jr. was important to the Civil Rights Movement in at least two main ways.
First, King was extremely important as a leader of the black community. King’s leadership and motivational skills were able to push the movement forward. They were also able to keep the vast majority of the African American activists from acting violently. King was able to persuade them to adhere to his philosophy of nonviolence.
Second, King was important because he was a visible leader who was relatively acceptable to the white community. The African American rights movement was always going to need support from white Americans. There were simply not enough minorities to gain rights without white help. Therefore, the movement needed leadership that could appeal to whites. If the movement had been led by someone along the lines of Malcolm X, the white community would have been much less likely to support it. Therefore, King was key to the movement.
King, then, was important to the Civil Rights Movement because he was able to motivate blacks while, at the same time, being relatively acceptable to many whites.