And, like Andromeda, the sonnet sweet
Fetter'd, in spite of painéd loveliness;
Let us find out, if we must be constrain'd,
Sandals more interwoven and complete
To fit the naked foot of Poesy;
Let us inspect the lyre, and weigh the stress
Of every chord, and see what may be gain'd
By ear industrious, and attention meet;
Misers of sound and syllable, no less
Than Midas of his coinage, let us be
Jealous of dead leaves in the bay wreath crown;
So, if we may not let the Muse be free,
She will be bound with garlands of her own.
Poets were traditionally given garland crowns to represent their status. 
 Keats wants to bind the muse of Poetry with the constraints of form he was had to deal with. 
 #That’s why this sonnet is irregular in it’s rhyme scheme.