Should I use additional id values as unique values that only applies in junction tables?

I have created three tables called person, metadata_image and person_image.

person table contains info about people.
person_id
person_name
person_bio

metadata_image table stores the images.
image_id
image_url
image_type
image_size
date_uploaded
importance (if importance equals to 1, I use that image as cover picture)

person_image has foreign keys from person and image tables.
person_id
metadata_image_id

Additional image :

Should I add a third column like person_image ID as a unique and auto increment value or is my structure okay as it is?