I get asked this a lot at film nights, and my go-to is always to check streaming aggregators first. If you mean the classic sci-fi/horror film 'The Thing from Another World' (1951) or the Carpenter cult classic 'The Thing' (1982), availability hops around. Right now, those titles often show up on services like the Criterion Channel, Shudder, or
Paramount+ in the US — but sometimes they're only rentable on platforms such as Apple TV, Google Play, Prime Video, or Vudu.
Another route I use is library-backed streaming: Kanopy and Hoopla sometimes carry restored classics or the more modern entries, and you can access them free with a library card. If you want the absolute highest quality or bonus extras, look into buying a Blu-ray or a Criterion edition, because collectors’ releases often include restorations and commentaries you won’t find on streaming.
Bottom line: plug the exact title into a site like JustWatch or Reelgood for your country, then decide whether you want to stream via a subscription or rent/buy. It saves time and keeps things legal — plus, hunting down a good Blu-ray edition can be oddly satisfying.