Literary devices such as similes and metaphors are used in "The Highwayman" to establish an ominous mood.

The first stanza relies heavily on the use of metaphors.

The wind was a torrent of darkness.

Of course, the wind itself can't be dark. But through this comparison, the tone is immediately set. This isn't the calm breeze of a summer's day. Darkness abounds, and it is further modified by the use of "torrent," which connotes a sense of being out of control or wild.

The moon was a ghostly galleon.

In this comparison, the moon is much like an old, sailing ship. This comparison is interesting because the moon's typical role has been shifted. Often used to provide guidance to sailors, the moon is seen as a constant source of direction, being steadfast and reliable. However, in this comparison the moon itself needs direction, finding itself in "cloudy seas." It is also described as "ghostly," adding to the eerie sense of foreboding as the poem opens.

The road was a ribbon of moonlight.

This third metaphor in three successive lines again adds to a sense of confusion. Not indicating a straight path, the road twists in ribbons in the moonlight. This same moonlight has been described as "ghostly" in the previous line; therefore, anyone who travels on this road is likely to encounter conflict.

The highwayman is shot near the end of the poem, and a simile (which uses like or as in a comparison) is used to show how he died:

When they shot him down on the highway,

Down like a dog on the highway

As with most poetry, the English poet Alfred Noyes' "The Highwayman" displays numerous examples of metaphors and similes, the latter being distinguished by the use of the words "like" or "as" in drawing comparisons between two unrelated objects or concepts. Metaphors, in particular, are simple to identify in Noyes's poem, which tells the tragic story of love interrupted by jealousy, tyranny and terror. With such a theme as Noyes employs in "The Highwayman," the comparisons he uses cover a range of emotions.

Examples of metaphors occur in the opening stanza of "The Highwayman," as Noyes establishes the tone from which to relate the story of love between the titular figure and Bess, "the landlord’s black-eyed daughter:"

The wind was a torrent of darkness among the gusty trees.   

The moon was a ghostly galleon tossed upon cloudy seas.   

The road was a ribbon of moonlight over the purple moor.

Similes and metaphors are literary devices called figures of speech that compare two unlike or dissimilar things to make a description more vivid or visual for the reader.  A simile uses the words “like” or “as” to make the comparison, a metaphor doesn’t use “like” or “as”.

Here’s a list of similes and metaphors from throughout the poem, “The Highwayman”  by Alfred Noyes.

The wind was a torrent of darkness among the gusty trees.  (metaphor) 

The moon was a ghostly galleon tossed upon cloudy seas.  (metaphor) 

The road was a ribbon of moonlight over the purple moor,   (metaphor)

 His eyes were hollows of madness, his hair like mouldy hay,  (metaphor/simile)

 Dumb as a dog he listened, and he heard the robber say—(simile)

 His face burnt like a brand (simile)

 When the road was a gypsy’s ribbon, looping the purple moor (metaphor)  

 Her face was like a light. (simile)

 Down like a dog on the highway (simile)