In Volume 2, Book 12, Chapter 4, Launcelot (banished by Guenever from Arthur's court) wanders bedraggled into the city of Corbin. The narrator uses a simile to highlight the dramatic irony of Launcelot's concealed identity:
And when Sir Castor was made knight, that same day he gave many gowns. And then Sir Castor sent for the fool – that was Sir Launcelot. And when he was come afore Sir Castor, he gave Sir Launcelot a robe of scarlet and all that longed unto him. And when Sir Launcelot was so arrayed like a knight, he was the seemliest man in all the court, and none so well made.
Launcelot has been wandering for a while, ever since he was tricked into appearing unfaithful to Guenever. He has lost some of his senses. Between his ragged appearance and his mental state, no one at Corbin recognizes him for the knight he is. Instead, they take him for a "fool." At the time Malory was writing, a fool would have been understood as a kind of entertainer whose performances could provide not only comic relief, but also lighthearted ironic commentary on society and politics. Launcelot is dressed up "like a knight" at the celebration of Sir Castor's knighthood because it is amusing for people in attendance to see a lowly fool in the garb of the "seemliest man in all the court." Dramatic irony adds another layer of amusement for the reader. While the characters really believe Launcelot to be a fool, the reader knows that there is no need for a simile. Launcelot in fact is a knight: to be dressed up like one is to be dressed up like himself.
At the same time, Launcelot is inhabiting the role of the fool perfectly. By donning knight's clothes, he helps highlight the fact that the people at Corbin don't understand what really makes a knight. Knights are governed by a complex chivalric code that their behavior ought to reflect, no matter what they are wearing. Gareth of Orkney, for example, shows up in Arthur's court dressed like a servant and spends an entire book proving that he is an excellent knight before he will reveal to anyone that he is in fact one of Arthur's nephews. The reader who has been keeping up with all of Malory's knights is thus in on another secret that the characters in Corbin are not -- the secret of what makes someone a knight.
In Volume 2, Book 13, Chapter 19, Launcelot wakes up from a dream-vision that he saw the Sangreal but could not move towards it. He hears a voice that uses three similes to describe him:
Right so heard he a voice that said, ‘Sir Launcelot, more harder than is the stone, and more bitter than is the wood, and more naked and barer than is the leaf of the fig tree; therefore go thou from hence, and withdraw thee from this holy place.’
The voice tells him first that he is "harder than stone," then that he is "more bitter than [...] wood," and finally that he is "more naked and barer" than a fig leaf. All of these comparisons lead up to the voice banishing Launcelot from "this holy place." Launcelot has trouble interpreting the voice and the dream-vision, but it seems that because he is more stone-like than stone, more wood-like than wood, and more leaf-like than a fig leaf, he is unfit to stay in the sacred place where the Sangreal just appeared in his very own dream-vision.
Launcelot goes to a hermit who explains to him what all these similes mean. The voice compared him to a stone because his sinful ways are so cemented that they haven't been worn down by any "goodness that God hath sent thee." It compared him to bitter wood because his sin is rotting him from the inside out like death rots a tree trunk. The voice compares him to a fig leaf because of a story in which Christ curses a fig tree to bear only leaves, never fruit. Like this tree, Launcelot is devoid of "fruit" (which, according to the hermit, means "good thought" and "good will"). This harsh judgment explains why Launcelot could not touch the Sangreal in his dreams: he is not good or faithful enough. Whereas Launcelot was once the greatest knight of the Round Table, he is now looking downright unworthy in comparison to his much more faithful son, Galahad.
Still, all hope is not lost. Seeing the dream-vision, hearing the voice make these comparisons, and listening to the hermit interpret them gives Launcelot an opportunity for self-reflection and redemption. He declares that he is going to "follow knighthood and do feats of arms" from here on out to try to absolve himself of his sins. Ironically, hearing himself described as hard, bitter, and bare seems to make Launcelot a little less hardened in his ways. He is able to undo the comparisons by healing himself from the inside out so that he might one day bear the kind of "fruit" the hermit describes. This is something a rotten tree could never do for itself.
In Volume 2, Book 14, Chapter 2, the Queen of the Waste Lands tells Percivale about how Merlin made the Round Table and informed the men about the future of the Grail quest. Merlin's prophecy reportedly involved a great deal of figurative language, including a metaphor and a pair of similes:
And men asked him how men might know them that should best do and to achieve the Sangrail. Then he said there should be three white bulls that should achieve it, and the two should be maidens, and the third should be chaste. And that one of the three should pass his father as much as the lion passeth the leopard, both of strength and hardiness.
The three white bulls (two maidens and one chaste) are a metaphor for the people who will find the grail (Percivale, Sir Bors, and Galahad). But this metaphor has multiple layers. White is usually associated with good and with devout Christianity in Malory's book. The white bulls themselves could represent any knights, as long as they are aligned with good and with God, and as long as one of them is "chaste."
The first real clue to who these three will be lies in the metaphorical comparison between "white bulls" and "maidens." Bulls are male, but the prophecy describes two of them as "maidens" (a feminine term). Maidens are women who have never been married, which should mean (according to the conventions of Arthur's court and Malory's day) that they have never had sex. There is no equivalent term for men because the same standard does not apply to them, so Merlin simply uses a metaphor to compare two of the "white bulls" (or good knights) to "maidens." A "maiden" knight is in fact so special that this status is part of what qualifies him to achieve the Sangreal. By the time Galahad and Percivale reach the Sangreal, they are the only two knights who qualify. It is notable that Sir Bors also qualifies to "achieve" the Sangreal even though he is merely "chaste," not strictly virginal. This means he has given into sexual temptation once but that it doesn't count against him enough to disqualify him. Just as Launcelot is lax and hypocritical about his own definition of fidelity, the book gives Sir Bors leeway that is rarely if ever offered to women.
The second clue that Galahad in particular will reach the Sangreal lies in the analogy claiming that one of the "white bulls" will surpass his father like a lion surpasses a leopard. The central father and son duo is Launcelot and Galahad, so this is a fairly clear indicator that Galahad will prevail. This analogy is a three-part simile. Merlin compares the relationship between the father and son in question to the relationship between a leopard and a lion. Within that comparison, he compares Launcelot to a leopard and Galahad to a lion. The lion comes up again and again in the book as a symbol of Christ, and Galahad's achievement of the Sangreal makes him a Christ-like figure. It is a flattering comparison. By contrast, Merlin compares Launcelot to a leopard. The leopard may be powerful and fast, but it cannot quite compete with the lion. This is the tragedy of Launcelot's character: he is extremely powerful and very good, but he is not a match for Galahad. However, he gets some redemption at the end of the book, when he is carried to heaven just as Galahad was.
