Retargeting
Retargeting is the practice of showing ads to people who have already interacted with you (visited your site, watched your video, opened your lead form but did not submit). For FE, retargeting is a high-ROI use of the last 10-20% of your ad budget.
Common FE retargeting audiences: people who visited your landing page in the last 14 days but did not submit, people who watched 75% of your video ad in the last 30 days, people who opened your lead form but abandoned it.
Retargeting CPLs are often 50-80% lower than cold-traffic CPLs because the audience is warmer. The catch is the audience size is smaller, so retargeting alone cannot be your primary lead source.
For native lead-form-only campaigns, the retargeting opportunity is "form opened but not submitted" — Meta tracks this and lets you build a custom audience from it.