fix metalness description

threejs/lessons/threejs-materials.md

@@ -169,8 +169,9 @@ have hard reflections whereas something that's not rough, like a billiard ball,
 is very shiny. Roughness goes from 0 to 1.
 
 The other setting, [`metalness`](MeshStandardMaterial.metalness), says
-how metal the material is. Metals behave differently than non-metals
-and so this setting goes from 0, not metal at all, to 1, 100% metal.
+how metal the material is. Metals behave differently than non-metals. For
+some reason this setting is un-intuitive and goes from 1, not metal at all,
+to 0, most metal like.
 
 Here's a quick sample of `MeshStandardMaterial` with `roughness` from 0 to 1
 across and `metalness` from 0 to 1 down.