How do I turn object into liquid

I CAN’T FIND TUTORIALS ON THIS!
I want to turn an object into liquid.
I’ve found tutorials on turning liquid into an object (control object) and I have seen an inflow simulation tutorials - where an object is emitting liquid.
But I can’t find any tutorials for turning an object into liquid. How do I do that?

On your liquid object, instead of having it as inflow, change it to Geometry.

Ok, how do I preserve the original materials from the object?
It just turns into default liquid material (glass/volume).
I want to preserve the materials that are on the object.