He told his men about the sirens, sharing what Circe had told him. gave them beeswax to plug their ears from their song.
So that he could hear their enchanting, tempting song, Odysseus instructed his men to tie him to the mast, and only lash him tighter no matter what he says until they are past the sirens.
Odysseus filled the ears of the sailors with wax before they tied him to the mast. The sailors couldn't hear the siren's song and Odysseus couldn't move.
Yes; the Sirens sang their enchanted song, and attempted to lure Odysseus and his men to their doom.
They Sing
He was warned about the Sirens by one of the spirits he met in the underworld.
The Sirens pose is they could trick Odysseus into going to their island and getting killed. The sirens could kill Odysseus's men and then Odysseus would end up going home with none of his men left.
The sirens are a danger that Odysseus and his men must pass to return home.