This material is completely procedural! That means it works with all models, no UV unwrapping is necessary (works with out-of-the-box generated coordinates), and there are no seams!

It works with both Cycles and Eevee although some features (like displacement) will only work properly in Cycles. Other than that create any lava you want using the custom sliders:

Coordinates: Plug in whatever coordinate system you want to use; generally you can just use generated which will work for any model (and if desired can be modified with a mapping node).
RockColor: The color of the non-lava material.
LavaAmount: The height of the lava relative to the rocks.
Falloff: Controls the transition between rock and lava.
Brightness: How bright the emission is for the lava.
NormalStrength: Intensity of the normal detail for the rocks.
Displace: Intensity of the (Cycles) displacement.
Distortion: The 'curl' of the lava.
Seed: Generates new version of the material.
AnimateX/Y/Z: Shift in the texture coordinates (to make the lava move and flow (you can also you seed for this)).

For installation just append the Lava Material into your project like you would any other; that is: go to File > Append > LavaMaterial.blend > Material > LavaMaterial