Definitions
Medal has one narrow definition. It refers to a flat piece of metal stamped with an inscription and given (1) as an award for placing high in a competition or (2) to commemorate brave performance in war.
Metal refers to any of a category of elements that usually have shiny surfaces, conduct heat and electricity, and can be melted. Metal is also a genre of music (short for heavy metal).
Mettle refers to (1) courage and fortitude, and (2) inherent quality of character and temperament.
A fourth word in this group of homophones is meddle, a verb meaning to intrude on another’s affairs or to tamper. It does not function as a noun, so it is easy to keep separate from the others.
Origins
Metal and mettle are closely related, with shared roots in the Latin metallum. In fact, they were variants of each other in their main senses until around the 17th century, when they began to differentiate. Medal, meanwhile, has a separate source—the French médaille, which in turn has roots in Italian and ultimately the Latin medallia. Since its use in Vulgar Latin, it has always related to coins. Meddle has a long history in English, but it derives ultimately from Latin words having to do with mixing.
Examples
At the same time the number of metal detectors in the country has increased to around 20,000, according to the National Council of Metal Detecting. [Telegraph]
He said his players showed their mettle despite conceding a 17-10 lead in the second half to lose the game 17-29. [Maidenhead Advertiser]
U.S. Air Force Colonel and Rehoboth Beach resident Carol Timmons has received the Bronze Star Medal. [WGMD Radio]
Those nations were tempted to meddle but hesitated largely because Seward scared them off with threats to declare war if they did so. [Wall Street Journal]
Given the metal and mining industry’s strong fundamentals in the fourth quarter, these stocks will likely report robust earnings. [The Street]
Trying circumstances often reveal our true mettle and expose our unspoken fears and hopes. [Indianapolis Star (article now offline)]
Anna Fenninger of Austria claimed the gold medal in the women’s super-combined event at the World Championships on Friday. [Sky Sports]
In case you haven’t heard yet, a documentary depicting the life of renowned metal vocalist Ozzy Osbourne is on the way. [UltimateGuitar.com]