Amazon’s ad-supported service Freevee (inside Prime Video) offers hundreds of free movies without a membership requirement — but even as a Prime member, you can watch them for free (with ads). Examples: Midsommar , The Social Network , Hotel Transylvania .
Here’s a short write-up on finding and watching (for Amazon Prime members): “Free Prime Video Movies” – What You Actually Get free prime video movies
On any movie page, if you see “Included with Prime” next to the price, you can stream it for free. Avoid titles marked “Rent $3.99” or “Buy $14.99” unless you want to pay. The Social Network