be on/upon one's mettle

1. 奋发; 准备尽最大的努力

We'll have to be on our mettle to win the game.

要在这场比赛中获胜, 我们得准备尽最大的努力。

put someone on his mettle

1. 考验某人; 激励某人

He was put on his mettle.

他受到考验。