I am one that would rather go with sir priest than sir knight: I care not who knows so much of my mettle.
— [To VIOLA] Your master quits you; and, for your service done him, So much against the mettle of your sex, So far beneath your soft and tender breeding, And since you called me master for so long, Here is my hand; you shall from this time be You master’s mistress.
There are no more uses of "mettle" in the play.
Show samples from other sources
The Trials are a test of my mettle.
Sabaa Tahir -- An Ember in the Ashes
But I will say, too, that for every man who showed no fear or hesitance, there were three or four or five others whose mettle was as unashamedly wan and mortal as yours or mine.