MacOS Monterey didn't have the most graceful launch for some users. According to 9to5Mac, Apple told YouTuber Rene Ritchie it fixed a firmware issue preventing some Macs with T2 security chips from starting. New upgraders who install Monterey will now get updated firmware alongside the OS. The T2 chip exists in most Macs released between 2018 and 2020.
Apple didn't say which systems were most likely to be affected. However, it said only a "very small number" of users ran into the problem.
Unfortunately, there's no easy way to recover if your Mac bricked as a result of the update. If you ran into trouble, you'll have to contact Apple technical support. It's not clear if you'll have to send your Mac in for service, but it's safe to presume this could sour your Monterey experience. As common as OS launch bugs may be, they're seldom this serious.