The character that appears with the helmet tries to hide your intentions or personality to others or yourselves. If the helmet is of anatomical lines and undecorated, then it reveals that practical thoughts are hidden and related with direct action. A beautifully decorated knight helmet can be interpreted that you hidden thoughts and desires are out of reality. You need to be more to the ground.
Knight helmet dream meaning
Read more about dreaming of Knight helmet in other dream meanings interpretations.