The Silver Surfer is many things, and stands as testament to how far the genius of Stan Lee and Jack Kirby could span: from the real life, "realistic" adventures of Spider-Man trying to make his rent, to the cosmic, philosophical tales of the Silver Surfer. The Silver Surfer existed on a cosmic level that was unknown in Marvel comics at that time, and not really touched even in DC comics. Despite his great power, he wasn't interested in fisticuffs, and fought even the greatest menaces with reluctance. He was, as suggested above, something of a Christ figure.
All of which has been commented on before, but I think an equally important issue to raise, that has not been addressed enough, is why the Silver Surfer doesn't wear any clothing. Any at all! He goes around totally naked, and no one ever acts very weird about it, or anything. I suppose that could be because often, when the Silver Surfer interacts with other super heroes, it means that something big is going down, and when Thanos is threatening to destroy the universe again, you can't worry about whether one of your important allies is, or is not, wearing shorts. Although, since Thanos threatens to destroy the universe with clockwork regularity, perhaps the curiosity of the Surfer's pantslessness would come to the fore. Although, for those not familiar with the appearance of the Silver Surfer, it should be pointed out that he exhibits no external genitalia, with the area being a smooth, gently rounded silver expanse.
More seriously, the Surfer's state of undress is interesting given the strictness of the Comics Code at the time when he first appeared. And although it was weakened throughout the coming decades and finally disposed of early in this decade, a nude character is still a rarity in comics. And yet, the external response to the Surfer's nudity seems to be as muted as the internal response. Perhaps that is because no serious comic book critic, if such a thing exists, would want to admit that they were not pondering the important cosmic and moral issues raised therein, but instead were staring at the Silver Surfer's crotch area, trying to figure out whether the line around his waist was the waistband of his shorts, some strange quirk of Zenn-Lavian anatomy, or purposely kept ambiguous. It should also be pointed out that artists have chosen to not go to lengths to either hide nor conceal the vital area of his anatomy. Artists don't usually go to great lengths to hide his groin behind shadows and body contortions, but neither does the Silver Surfer go around with his codpiece sticking proudly out. And, as I said before, the Silver Surfer exhibits no external genitalia, with the area being a smooth, gently rounded silver expanse.
I think that the Silver Surfer's nudity is not just an accident, but is tightly tied in to his character. He is, by all appearances, a neuter being, and his conduct is somewhat neutered. Despite having powers that outstrip any other hero on earth, the Surfer chooses not to use them. His metaphorical phallus is just as oblique as his physical one. His naked physique and lack of obvious gender identity set him apart from the other characters he interacts with, he is somewhat angelic in nature. If the Silver Surfer is indeed, a Christ figure, it would not do for him to have a flamboyantly coy codpiece. (Such an interpretation brings up other issues, such as whether a Christ figure would have a smooth, gently rounded silver expanse in the genital region, and whether the surfboard is a cross of some sort.) There are of course exceptions to this theory as Silver Surfer as divine eunuch: he has had at least three girlfriends, and despite his generally gentle temperament, he is not averse to occasionally displaying unfettered male fury. Also, cosmic stature does not usually go along with being unclothed in the Marvel Universe: even such abstract entities as Eternity and Death follow some social conventions about dress. And Eternity isn't even humanoid, instead being a field of stars that still remembers to put on his cape. Whether this departure from code is an example of nuance and diversity in portrayal amongst Marvel's writing and editorial staff, or just an example of sloppy and inconsistent writing, is left as an exercise for the reader.
So, after reading this, the reader is left either more enlightened, or left with the prospect of never being able to read another Silver Surfer comic without scoping out the Surfer's lack of external genitalia. I hope that the second result does not ruin too much comic reading pleasure.