Yeah it's Melkor (or Morgoth if you want to be pedantic).
Easy mistake to make as it's a common theme in Tolkien's work:
Big Evil Guy vs Little Good Guy.
Morgoth/Fingolfin, Sauron/Elendil (or Isildur!), Witch King/Eowyn, Shelob/Sam.... I could go on. See the pattern?
This thread raises an interesting point about how we visualise Tolkien's world when it isn't described in detail (or even what he mentions as metaphor eg. Balrog "wings").
For instance it is never written what Morgoth actually looks like (in detail), but neither does it say "He by no means had big chompy teeth and a scowly expression on his face. The Dark Lord did not look like that at all".
It leaves us to imagine some of the finer details, especially in the Silmarillion which is much more about "This big event happened over here, then that happened over there." [I'm trying to get around to reading the other texts that were compiled into it, maybe there is more detail there.]
Half the fun of reading this fantastic stuff is that we've all got a different image of what it describes.
Most of my fave art is whatever fits my mental picture the closest. This is also why I tell people to read the books before watching the films.... No-one ever does though!
![Rolling Eyes :roll:](./images/smilies/icon_rolleyes.gif)