metal / mettle are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
metal: (verb) cover with metal.
mettle: NA
metal: m·EH·t·ah·l
mettle: m·EH·t·ah·l
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)