The Lerp Node is amazing, I needed water damaged stone. So I took one of the starter content materials, scaled out the material, then went into photo shop after finding an image of water damage, lerp it into the base color with the outcome of the stone base color and BAM, water damaged stone. I figured this might be better in general discussion, but because this is a statement about materials, I figured this thread was appropriate.
Wait until you discover what you can do with it if you start animating the alpha texture for the lerp 
I used it to combine two moving water textures (with different speeds) and a grayscal noise texture (moving in the opposite direction) to create a nice water effect 
When messing around with that I actually accidentally maid a lava texture by using this random blend node, when I id that I used something called NormalFromHeightMapChaos and it made a pretty decent water effect as well. I honestly think that the most entertaining aspect about the engine is customizing your materials.
Edit I used the height from the normal node and it made the normal map pull to the front and kind of made this cool futuristic water node.
Nice But keep in mind that tehse nodes are very “expensive”.
It may be better to bake these into textures.