The sirens are a danger that Odysseus and his men must pass to return home.
They sang a beautiful song that would promise men happiness. It attracted men but once they got there, they would kill the men. Kirke told Odysseus to plug his mens ears with beeswax and she wanted...
Sirens were nymphs who lured sailors to their death with a bewitching song.
Book XII Scylla and Charybdis - The Cattle of the Sun
By temptation, the men also saw that Odysseus had a weakness.