We had someone ask (after the class) about the place where we read that Elijah would return, and I made mention that it was John the Baptist the prophesy was talking about and moved on. Let me explain a little better.
It is an interesting prophesy. The reason we see John the Baptist as Elijah is because Jesus implied it to the disciples. Look @ Matthew 11:7-15:
As John’s disciples were leaving, Jesus began to speak to the crowd about John: “What did you go out into the wilderness to see? A reed swayed by the wind? 8 If not, what did you go out to see? A man dressed in fine clothes? No, those who wear fine clothes are in kings’ palaces. 9 Then what did you go out to see? A prophet? Yes, I tell you, and more than a prophet. 10 This is the one about whom it is written:
“‘I will send my messenger ahead of you,
who will prepare your way before you.’[a]
11 Truly I tell you, among those born of women there has not risen anyone greater than John the Baptist; yet whoever is least in the kingdom of heaven is greater than he. 12 From the days of John the Baptist until now, the kingdom of heaven has been subjected to violence,[b] and violent people have been raiding it. 13 For all the Prophets and the Law prophesied until John. 14 And if you are willing to accept it, he is the Elijah who was to come. 15 Whoever has ears, let them hear.
Also in Mat 17 at the transfiguration we also see Elijah with Moses and Jesus. It is also widely believed that Elijah is one of the two witnesses in the book of Revelation, (with Moses). All of this is still within the prophesy, either at the first or second coming of Christ. One way to look at the instance of John being Elijah is that Jesus is saying this figuratively. He came "like" Elijah, calling out from the wilderness, as you said. Others believe He is the embodiment of Elijah himself. Either way it is a mystery that cannot be fully grasped. You will notice in Mat 17 that Jesus says again that Elijah presented himself as John (verse 12). The same scripture is described in Mark 9.
