Story is pretty minimal to nonexistent. It is pretty much almost a survival sandbox, with certain requirements (you need to kill bosses) to progress.

You can learn all about this on their website which I'm linking here for your convenience.
https://www.valheimgame.com/

If you like building, you will probably like Valheim. It has a very nice building system, that I come to like much more than the one in Conan. It's probably not as vast as pure building simulators, but it is pretty nice.

IronGate did a lot of things right with Valheim and unfortunately a few things wrong. This game drips atmosphere by the bucket load. The different environments are all beautiful and the lighting and weather is something to behold.

Just be aware that this is not a game for graphic snobs that can only stand ultra realistic graphics. The graphics are pixelated, but the environments are really beautiful, so you really forget that the models and textures themselves are rather crude (mostly, not all).