Hard metal would make little difference. It may cause more nicks in the blades but a 5 pound drone would be little different than a 5 pound bird. In fact most bird strikes never make it to the compressor stage. That big fan in front slings most bird parts away from the intake. Large hale is almost as hard as small metal parts and the airliner engines can fly though most hale. Keep in mind this is not true of business jets and military planes.