Good day Timothy5378!
According to Jesus, Elijah has already come:
From the days of John the Baptist until now, the kingdom of heaven has been subject to violence, and the violent lay claim to it. For all the Prophets and the Law prophesied until John. And if you are willing to accept it, he (John the Baptist) is the Elijah who was to come.
"The disciples asked Him, “Why then do the scribes say that Elijah must come first?”
Jesus replied, “Elijah does indeed come, and he will restore all things. But I tell you that Elijah has already come, and they did not recognize him, but have done to him whatever they wished. In the same way, the Son of Man will suffer at their hands.”
Then the disciples understood that He was speaking to them about John the Baptist.
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John the Baptist came as a type of Elijah, fulfilling Mal.4:5-6.