How many letters does the top answer for “not containing or resembling or characteristic of a metal” have?

The most common answer is nonmetal (8 letters).

Crossword clue: not containing or resembling or characteristic of a metal

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

nonmetal 8 letters wn-def

a chemical element lacking typical metallic properties

nonmetallic 11 letters wn-def

not containing or resembling or characteristic of a metal