故事是由主人公-----以实玛利走进“鲸鱼旅馆”的那一刻开始的，当晚，他被老板安排和一个名为“魁魁格”的大个子睡在一起，魁魁格是科科伏柯岛的王子，他有一手很好的叉鱼技术，魁魁格和以实玛利有着同样的志向——出海远航，做一名勇敢的水手。二人志同道合，就一起上路了，他们签约了一艘名为“裴廓德号”的捕鲸船
“裴廓德号”并不是一艘普通的船只，或许说“裴廓德号”的船长不是一个普通的船长吧。“裴廓德号”的船长名叫亚哈，他是一个瘸子，他的一条腿被一只名叫莫比迪克的白鲸给咬掉了。为此，亚哈船长与莫比结下了仇，并且发誓：誓死杀掉莫比。但是和白鲸作对自然不是什么好事，他们最后还是输了，并且输的一败涂地。船破人亡，唯一幸免的以实玛利因为一副棺材而获救，那个本来是给魁魁格准备的棺材，最后成为以实玛利的救命物，这实在是一个讽刺，一个对“裴廓德号”的讽刺，对所有船员的讽刺！
在这个故事中，就是因为他的固执，让很多抱有梦想的人葬身于大海从一开始，亚哈船长就在为自己挖坟墓，从他捕杀莫比那一刻开始，他向莫比身上的投的鱼叉越多，他给自己挖的坟墓就越深，直到最后，他不仅自己跳了下去，还拉带这好多人一起跳下那个又深又“恐怖”的坟墓。那些与白鲸的斗争都是无意义。亚哈船长看上去很令人钦佩，因为他的勇敢，因为他的什么什么，但那是莽撞，另类的莽撞！从文章中不是没有看到大家在劝他放弃这个念头，“拉吉号”的船长劝过他，大副斯达巴克也劝过他，可他就是不听啊，到了最后，他似乎是完全疯掉了。
其实，只要你放弃它，不要复仇，你就不会消逝你那勇敢的生命！

Moby-Dick is a highly symbolic work, and is interesting in that it also addresses issues such as natural history. Other themes include obsession, religion, idealism versus pragmatism, revenge, racism, hierarchical relationships, and politics.
Symbolism
All of the members of the Pequod's crew have biblical-sounding, improbable, or descriptive names, and the narrator deliberately avoids specifying the exact time of the events and some other similar details. These together suggest that the narrator—and not just Melville—is deliberately casting his tale in an epic and allegorical mode.
The white whale itself, for example, has been read as symbolically representative of good and evil, as has Ahab. The white whale has also been seen as a metaphor for the elements of life that are out of our control, or God.[citation needed]
The Pequod's quest to hunt down Moby-Dick itself is also widely viewed as allegorical. To Ahab, killing the whale becomes the ultimate goal in his life, and this observation can also be expanded allegorically so that the whale represents everyone's goals. Furthermore, his vengeance against the whale is analogous to man's struggle against fate. The only escape from Ahab's vision is seen through the Pequod's occasional encounters with other ships, called gams. Readers could consider what exactly Ahab will do if he, in fact, succeeds in his quest: having accomplished his ultimate goal, what else is there left for him to do? Similarly, Melville may be implying that people in general need something to reach for in life, or that such a goal can destroy one if allowed to overtake all other concerns. Some such things are hinted at early on in the book, when the main character, Ishmael, is sharing a cold bed with his newfound friend, Queequeg:
... truely to enjoy bodily warmth, some small part of you must be cold, for there is no quality in this world that is not what it is merely by contrast. Nothing exists in itself. If you flatter yourself that you are all over comfortable, and have been so a long time, then you cannot be said to be comfortable any more.
— Moby-Dick, Ch. 11
Ahab's pipe is widely looked upon as the riddance of happiness in Ahab's life. By throwing the pipe overboard, Ahab signifies that he no longer can enjoy simple pleasures in life; instead, he dedicates his entire life to the pursuit of his obsession, the killing of the white whale, Moby-Dick.
A number of biblical themes occur. The book contains multiple implicit and explicit allusions to the story of Jonah, in addition to the use of certain biblical names (see below).
Ishmael's musings also allude to themes common among the American Transcendentalists and parallel certain themes in European Romanticism and the philosophy of Hegel. In the poetry of Whitman and the prose writings of Emerson and Thoreau, a ship at sea is sometimes a metaphor for the soul.