"This is Halloween" is the opening song from the movie The Nightmare Before Christmas. It makes a great introduction to Halloween, especially setting the mood. Note that this song is not to be confused with the Marliyn Manson song of the same name!
I found the karaoke version on Youtube, so it has the lyrics as subtitles. And the words are actually not as I thought it might be. I do wish it referenced more traditional monsters in the lyrics because I'm having trouble thinking of ways to make them use "Frankenstein", "werewolf".
This video will make a good opening activity I think. Or something extra to have under your belt. I did a cloze/gap-fill exercise of the lyrics
You can also have students watch and list all the scary monsters they see. Introduce the idea of the Boogey man, the monster who hides in the closet or under the bed. Ask if their culture has a similar catch-all monster. Ask if scary and creepy things can ever be fun? Discuss the lyrics. Why do the monsters say they aren't mean? Are the things mentioned in the song scary? Like clowns that have tear-away faces? Or is it pretty funny over all?