Many rabbinical studies programs require you to study in Israel for a year to improve your command of Hebrew. Your stay there may give you access to certain unique learning resources. It also deepens your commitment to the Jewish people.
Whether or not your program includes time in Israel, you will need to be proficient in Biblical Hebrew. You also may study Mishnaic Hebrew and Aramaic in order to read the classic texts. Learning these languages is also part of yeshiva study.