Maelifjell is for sure one of the absolute highlights, Iceland has to offer. If you have a proper (!!!) 4 wheel drive car, sou should definitely take the time and drive up from Grafakirkja or Gluggafoss. Be aware that you'll have to cross some rivers or heavy rock fields without having too much clue, how deep the water is and where the right spot for a crossing is.
If you make it however, its mind-blowing: This green mountain in the middle of a huge black field of volcanic ash, framed by huge glaciers in the background.
Mount Mælifell is a wonderful place with a marvellous view all around it. the now inactive volcano is left standing by itself surrounded by sandy land and many small streams. I highly suggest a visit to this wonderful land mark which I believe would be the nicest place with the best view in all of Iceland.