Key to my heart

If you want the key to my heart
you will have to treat me true
If you treat me with love and respect
my love will be just for you

but if you dare to break it
you will have to see
a horrible, nasty monster
which is the dark side of me

cause if you try to hurt me,
it will protect me through and through
cause the one thing that it knows about me, is i'm desperatly in love with you