‘O, she doth teach the torches to burn bright’ is a famous speech spoken by Romeo in Act I Scene 5 of Shakespeare’s Romeo and Juliet. But what does he mean by this speech? Although the meaning may appear to be straightforward, when viewed in the context of the play Romeo’s words shed some considerable light on his character. Before we analyse the ‘O, she doth teach the torches to burn bright’ speech, though, here’s a reminder of what Romeo says:
O, she doth teach the torches to burn bright!
It seems she hangs upon the cheek of night
Like a rich jewel in an Ethiop’s ear;
Beauty too rich for use, for earth too dear!
So shows a snowy dove trooping with crows,
As yonder lady o’er her fellows shows.
The measure done, I’ll watch her place of stand,
And, touching hers, make blessed my rude hand.
Did my heart love till now? forswear it, sight!
For I ne’er saw true beauty till this night.
First, the context of Romeo’s words: Romeo is at the Capulets’ masked ball, with his friend Mercutio. Mercutio has just told Romeo about a fairy named Queen Mab who enters young men’s minds as they dream, and makes them dream of love and romance. At the masked ball, Romeo spies Juliet and instantly falls in love with her; she also falls for him. ‘O, she doth teach the torches to burn bright’ is Romeo’s first response to clapping eyes on Juliet.
It’s worth dwelling on this image for a moment. ‘O, she doth teach the torches to burn bright’: i.e. the torches don’t actually seem to be all 
that bright at all, when compared with the brightness and radiance of Juliet’s beauty. ‘Teach’ here is a bit like ‘teaching someone a lesson’ or ‘schooling’ someone: it’s got an air of competition to it. Romeo is saying that the (poor, dim) torches could learn a thing or two from Juliet about how to shine brightly.
The rest of Romeo’s speech is an elaboration of this idea. Because everything else around Juliet seems dull by comparison (plus it is, after all, literally night time), she – this beautiful bright thing – is like a rare and sparkling jewel hanging from the ear of an Ethiopian. (‘Ethiop’ – actually a more general term in Shakespeare’s time used to denote a black person from Africa, not just Ethiopia – is used deliberately of course to underscore the contrast between the dark skin of a person from Ethiopia and the brightness of the jewel; we’ll gloss over what this says about ‘bright/light = beautiful’ and ‘dark(-skinned) = dull’, and just say that, obviously, in Shakespeare’s time this would not have been viewed in the same way as we view it.)
Juliet’s beauty is ‘too rich for use’ because it’s none of your ordinary common-or-garden beauty: it’s like the finest jewels that are too precious to wear out and about all the time. The image of the ‘snowy dove’ flying with a flock of ‘crows’ continues the contrast between bright, pale Juliet (pallor being a sign of beauty in the Elizabethan era) and the mundane dullness and darkness of everything that surrounds her. Juliet’s ‘fellows’ are her friends: Romeo isn’t being very polite about Juliet’s female companions!
The ‘measure’ is the dance that is being performed as Romeo speaks these words: once this dance is over, he says, he will go up to her and touch her hand (as dancing partners might do before dancing together), and thus make ‘blessed’ his own poor hand by coming into contact with hers. Romeo concludes his speech by asking rhetorically whether his heart really did love anyone before he met Juliet. The answer, of course, is a big ‘No’. He ‘forswears’ or rejects any notion that he truly loved anyone (e.g. Rosaline) who came before Juliet. Now, though, he has seen true beauty, and its name is Juliet.
‘O, she doth teach the torches to burn bright’ is obviously somewhat over-the-top language, and it’s worth bearing in mind the comment of T. J. B. Spencer, in his notes to Romeo And Juliet (Penguin Shakespeare)
