started recording carreer 1968 and was already a big star when Queen started. After Free he refused Deep Purple's offer to replace Gillan and formed Bad Co with million selling success. He was a role model for several singer's - e.g. Coverdale (compare some Free ballads with D.C.'s ones).
His voice is bluesy, souly, hard rock at the same time. He became famous due to his VOICE and super masculine appearance at the stage - he did not need any special effects and lights, he just sang.
He also had "raised microphone stand" as a trademark(see e.g. a cover of Free album Hertbreaker and compare with Freddie).
He is one of the greatests, but I am still unsure if his style can be fitted in Queen.