Oliver Wendell Holmes's "Old Ironsides" is three-stanza poem written as a tribute to the frigate, the USS Constitution. Holmes's poem contributed to the move to prevent the ship from being decommissioned, proving the old adage that "the pen is mightier than the sword." It is now the oldest commissioned ship in the world that is still afloat. There is little question that Holmes's use of metaphors and other figurative language certainly helped to create an emotional response that contributed to the saving of the USS Constitution.
Most of the metaphors, or unstated comparisons, have already been mentioned in the previous post. However, there is the one about the sea as the "grave" for ships in line 20. This metaphor suggests that this important ship would simply rust at the bottom of the ocean where it would be buried from view and forgotten, rather than remaining as a historical monument of America's many victories. This metaphor, therefore, contributes to the persuasive power of the poem that the vessel should be restored and kept as a memorial to the resilience of America to the British.
Another metaphor is the name of "Old Ironsides" that is given to the USS Constitution. This comparison of the ship's construction to the structure of iron connotes strength and indomitable force.
Of course, the entire poem is an extended metaphor, a comparison between two unlike things--the American warship and its being an American icon-- a comparison whose significance continues throughout a series of lines in the poem.