True, I talk of dreams,

Which are the children ,of an idle brain,
Begot of nothing but vain fantasy,
Which is as thin of substance as the air
And more inconstant than the wind, who wooes
Even now the frozen bosom of the north,
And, being anger’d, puffs away from thence,
Turning his face to the dew-dropping south.

This quote uses a metaphor about dreams or illusions as state One the first line “True I talk of dreams.”This phrase was said when Romeo was talking to Mercutio about Roseline.Mercutio retorts saying that dreams pass by like the wind ” And more inconstant than the wind,who wooes.” Mercutio is trying to express that you should not be obsessed over Roseline.