According to the Rambam, the Messiah will be a king who will arise from the line of David. He will be a great Torah sage. He will compel Israel to walk in the way of the Torah, fight the wars of G-d, rebuild the Temple in Jerusalem, gather in all the exiles of Israel and then motivate the entire world to serve G-d together.

In his Mishneh Torah the Rambam also says Messiah will build the Temple. Rambam is right again, according to Tenakh: Messiah is the true Temple builder.