a person’s ability to cope well with difficulties; spirit and resilience:the team showed their true mettle in the second half
be on one's mettle
be ready or forced to do one’s best in a demanding situation:Saturday’s game will be a tricky one and we’ll have to be on our mettle from the start
put someone on their mettle
(of a demanding situation) test someone’s ability to face difficulties:there were regular public meetings where local MPs were put on their mettle and remorselessly pilloried