prove (one's) mettle(redirected from prove mettle)
prove (one's) mettle
To prove that one has endurance and strength of character, or the necessary skills, abilities, or traits to succeed in something. You may be the youngest lawyer in the firm, but you certainly proved your mettle in that high-profile murder case. The new CEO proved her mettle when she joined the company in 2012 and completely restructured their dying mobile phone division into the powerhouse it is today.