Failed to connect to lvmetad - Stuck on boot

I had a very similar experience, not sure if it'll help you though. My computer had some updates installed, needed a reboot but hey, nobody got time for that. Well along came a power outage and forced me to reboot. When I turned on my machine, I got just the same message you saw. Crap. I couldn't even get into virtual terminals 1 or 2 either which was really weird. Anyway, I somehow found your post and read that switching the kernel version made everything work. So I went and tried that out and sure enough, what you said applied to me too.

With my primitive knowledge of linux commands, I did get an idea of how to fix this. So I rebooted into the newest kernel, then switched to the virtual terminal ctrl+alt+f3 <- had to use the third because 1 and 2 weren't working. From here I ran sudo apt-get update && sudo apt-get upgrade -y to get everything up to date. Then ran sudo apt-get autoremove to remove the older kernels. Then I re-installed the current kernel (get the version from uname -r) and then I ran sudo apt-get install --reinstall linux-image-4.13.0-32-generic to reinstall the current kernel and rerun all the building of things that might not have been run since I didn't switch to this kernel properly. Finally, I restarted again.

After the restart I was having the same problem still. Welp, maybe it has to do with my graphics drivers? So I went ahead and purged my nvidia drivers sudo apt-get purge nvidia-* and reinstalled the drivers sudo apt-get install nvidia-387 ~ Granted, I don't know what version of their driver I should be using, nvidia afik doesn't have just a standard package that you can install that follows the latest - but this one installed just fine for me... After that super slow install, I restarted again.

And my computer came back to life. Woohoo. I genuinely hope this helps someone. It took me 4 hours of frustrated pounding to get my desktop back and I really hope I can save someone else from that. Thanks for your post and your update, you gave me the lead that I needed to solve this for myself.

The accepted answer helped me quite a lot (thank you!)

Though in my case neither booting with an older kernel nor the nvidia driver could solve it... it just turned out my disk had run full (as I saw with df). I could delete files by booting into recovery mode and from then on boot normally again :)

I hope this hint is useful to anyone stuck in this situation