If you're looking to reach individuals beyond those who've explicitly liked your Facebook Page or followed your Instagram profile, then building Facebook audiences using Facebook Interests is a great targeting option for you.
People are included in this target audience based on what they’ve included in their profiles, as well as the Pages, Groups, and other things on Facebook they’ve connected with. This includes sections like interests, activities, favorite music, movies, and TV shows.
The availability of the brand as an “interest” is incredibly arbitrary; Facebook will add and remove certain “interests” without notifying anyone.
For example, acts with millions of followers on Facebook and Instagram such as “Marshmello” are unavailable as an interest to target.
If an interest is unavailable in Facebook, it will also be unavailable to target in the service.
To target interests on the service, begin by pressing “Add New” or “Change Template,” then “Facebook,” then “Facebook Interest Audience,” followed by selecting the interest name under the “Advanced Targeting” section in the “Share at least ONE of the following Interests” field:
Sometimes your brand will not show up as an interest. If this is the case, two of the options you can explore are using more advanced custom audiences or inputting brands related to yours as interests.