In Chapter 18, the narrator interrupts the story to give his thoughts on the way that men treat women in relationships. He uses metaphor and simile to get his point across:
We are Turks with the affections of our women; and have made them subscribe to our doctrine too. We let their bodies go abroad liberally enough, with smiles and ringlets and pink bonnets to disguise them instead of veils and yak-maks. But their souls must be seen by only one man, and they obey not unwillingly, and consent to remain at home as our slaves—ministering to us and doing drudgery for us.
By the narrator's perspective, the English are metaphorically Turkish when it comes to their treatment of women—a likely reference to the Ottoman sultan's practice of keeping a harem of women in his court, some of whom were enslaved. The narrator builds upon this comparison more explicitly with the closing simile of the passage: women "remain at home as our slaves," imprisoned by the possessiveness of their husbands and forbidden to ever truly go free.
This is a scathing critique of the institution of marriage as a tool for setting repressive gender expectations on women, and by taking this stance early on in the novel, the narrator primes the reader to look out for challenges to this norm. Sure enough, the story of Becky's interlocking romantic and social escapades constitute a major rebellion against this stifling marital environment: although occasionally destitute and often deceitful, Becky's soul remains free.
In Chapter 25, the narrator continues to whisk the reader around the interlocking stories of Vanity Fair somewhat out of order, and this ultimately maximizes each story's dramatic effect. The narrator uses a lengthy and somewhat convoluted simile to emphasize his privilege in knowing the bigger picture and delivering it to the reader in the best possible fashion:
As you behold in Her Majesty’s drawing-room, the ambassadors’ and high dignitaries’ carriages whisk off from a private door, while Captain Jones’s ladies are waiting for their fly: as you see in the Secretary of the Treasury’s antechamber, a half-dozen of petitioners waiting patiently for their audience, and called out one by one, when suddenly an Irish member or some eminent personage enters the apartment, and instantly walks in to Mr Under-Secretary over the heads of all the people present: so, in the conduct of a tale, the romancer is obliged to exercise this most partial sort of justice.
Just like various important people have the authority to bypass the general public in order to discuss important matters with other important people, the narrator has the authority to move around the story and bypass certain events to keep the reader engaged. "Our history," the narrator offers earlier in this same aside, "is destined in this Chapter to go backwards and forwards in a very irresolute manner"—and the narrator believes "we have occasion to step back to yesterday, so that the whole of the tale may get a hearing."
This is one of countless examples of the narrator's unreliability in Vanity Fair—he'll tell the reader a compelling story, to be sure, but it might not be the most straightforward one, and he might not tell it the way it actually happened.
In Chapter 36, the narrator treats the reader to an engaging description of how, exactly, the Crawleys have been able to sustain a lavish lifestyle with no discernible source of income (the chapter is called "How to live well on Nothing a Year"). While Becky has her own duplicitous means of securing cash, Rawdon is quite the gambler. He finds quite a lucrative business in card games, and Thackeray describes his bewildering success in that department in a simile that alludes to the famous reputation that the Duke of Wellington held amongst the French:
And as the French say of the Duke of Wellington, who never suffered a defeat, that only an astonishing series of lucky accidents enabled him to be an invariable winner; yet even they allow that he cheated at Waterloo, and was enabled to win the last great trick: so it was hinted at headquarters in England, that some foul play must have taken place in order to account for the continued success of Colonel Crawley.
As the man who defeated Napoleon, the French have good reason to dismiss the Duke of Wellington as a lucky, rather than a brilliant, general—for the sake of French morale, at the very least. In much the same way, Crawley's opponents can't quite understand how he has such success at the card table.
Thackeray attempts to connect his narrative with the historical context of the Napoleonic wars throughout the novel, but, as is the case here, that connection can be heavy-handed to the point of silliness. On the one hand, this simile gives Rawdon a slice of Wellington's own historical grandeur, but on the other, it serves to make Rawdon's attempts to stay financially afloat feel all the more pathetic.
Vanity Fair contains a wide variety of vivid, often hilarious descriptions of satirically vapid upper class conversation. In Chapter 46, that conversation reaches new lows as a Mrs. Frederick Bullock drones on about her family—and then bids adieu with a horrific kiss that Thackeray enhances using simile:
My darling Frederick must positively be an eldest son; and – and do ask papa to bring us back his account in Lombard Street, will you, dear? It doesn’t look well, his going to Stumpy & Rowdy’s.’ After which kind of speeches, in which fashion and the main chance were blended together, and after a kiss, which was like the contact of an oyster – Mrs Frederick Bullock would gather her starched nurselings, and simper back into her carriage.
Although an inconsequential moment to the plot of the novel, this simile that compares Mrs. Bullock's kiss to the slimy touch of an oyster is visceral and revolting—so too is the meaningless, self-involved small talk that precedes it. Satirical details like these, which exaggerate the behavior of the English elite in order to better expose their ridiculousness, are essential bits of scaffolding that enable Thackeray to transform his vision of English society into the vast literary world of Vanity Fair.
Thackeray opens Chapter 48, in which Becky at last gains an audience with the king, with a lengthy simile that describes the significance of such an event in the life of an upper-class woman:
[…] we know that no lady in the genteel world can possess this desideratum [for virtue], until she has […] been presented to her Sovereign at Court. From that august interview they come out stamped as honest women. The Lord Chamberlain gives them a certificate of virtue. And as dubious goods or letters are passed through an oven at quarantine, sprinkled with aromatic vinegar, and then pronounced clean, many a lady whose reputation would be doubtful otherwise and liable to give infection, passes through the wholesome ordeal of the Royal presence, and issues from it free from all taint.
This simile compares the effects of a royal audience with the effects of laundering dirty linens—or linens that may have been used in the treatment of a diseased patient. Such is the power of the king's attention: even a lady with such a bad reputation as to be practically contagious—here the infectious language spills over into the description of the audience itself—is "cured" of her social malady through this interaction.
There is an unmistakably satirical tone at work in the narrator's description of these effects: it is as though he is mimicking the existential stakes of a royal audience, as perceived by the ladies who seek one, in order to more efficiently mock it—although an audience with the king may be a temporary salve for Becky's toxicity, it is unlikely to cause meaningful change in the content of her character.
