Metonymies are very common in our every day speech and in Biblical literature. We often substitute ideas for people or places for things in order to keep our speech and writing from becoming stale and repetitive.

In the phrase:

"The orders came directly from the White House"

"White House," an inanimate object is used in place of a person, the President of the United States.

"He is addicted to the bottle"

In this phrase, "the bottle," is used in place of  another impersonal object, alcohol. These kinds of metonymies are commonly used in our everyday language.  Because metonymies are used so frequently, native readers or listeners are often unaware of their usage. But those not familiar with the customs and language of a particular culture can become confused with certain unclear metonymies.

In interpreting Scripture, correctly identifying a metonymy and the author's intended referent can be important. Usually a metonymy will not drastically change the meaning of a passage, but recognizing the metonymy gives added insight and clarity to the passage.

In the dramatic scene of Jesus trial before Pilate, the Jews shout out:

His blood be upon us and our children
Matt. 27:25

Here the Jews do not want the literal blood of Jesus on their bodies; rather they are using "blood" in place of the guilt or responsibility of his death. The use of a figure of speech makes intensifies their statement while retaining the same meaning.

Make a joyful noise unto Go, all ye lands.
Ps. 66:1 (KJV)

In this last example, it is obvious that "land" cannot audibly praise God, so "all ye lands" (or "all the earth", NASB, NIV) refers to "all peoples in all lands."