Henry is a figurative writer who uses several metaphors in his speech. He says, for example, that the colonists are listening to "the song of that siren till she transforms us into beasts." The song of the siren is an allusion to Greek mythology and refers to beautiful women who lured sailors to wreck their ships by singing enchanting songs. Henry uses both an allusion and metaphor in this sentence, as he refers to the colonists' willingness to go astray by listening to the British.
Later, he says, "Are we disposed to be of the number of those who, having eyes, see not, and, having ears, hear not." This is a metaphor in which he likens the colonists to people who will themselves to be deaf and blind, though they have the means to see and hear. In other words, he says the colonists are willing themselves to be ignorant by not paying attention to what the British are doing.
Using metaphors referring to slavery (as the educator above also notes), he says of the British army and navy, "They are sent over to bind and rivet upon us those chains which the British ministry have been so long forging." He likens the restrictions of the British to chains that bind the colonists and limit their freedom. He then asks the following:
"Shall we acquire the means of effectual resistance, by lying supinely on our backs, and hugging the delusive phantom of hope, until our enemies shall have bound us hand and foot?"
In this metaphor, he compares the colonists to people who lie on their backs and hug an elusive vision of hope while the British enslave them. These metaphors are both inventive and powerful.