As keen as mustard or as keen as a kitten
A simile.
A metaphor
Yellow mustard is a prepared mustard. Dry mustard, or mustard flour is not prepared mustard.
As quick as a wink is a simile. ----
It is a simile.
simile It is an example of a simile (uses like or as). A simile in itself though is a type of metaphor.
simile
mustard2 syllables:bustard, clustered, flustered, mustard, mustered3 syllables:black mustard, field mustard, great bustard, hedge mustard, leaf mustard, white mustard, wild mustard4 syllables:Chinese mustard, garlic mustard, spinach mustard, sulfur mustard, table mustard, tansy mustard, tower mustard5 syllables:buckler mustard, Indian mustard, mithridate mustard, nitrogen mustardfrom: rhymezone.com
that man
Sweet Mustard is sweeter than Plain Mustard.
It is a similie as you are comparing (something) to how sly the fox is. A similie uses the words "like or "as".