[subject] + 必将 + [verb phrase]
必将 is 必 "certainly" plus 将 "will": a firm prediction about the future. It goes before a verb phrase and sounds like a speech, an editorial or a report's conclusion.
The outcome is often hopeful – success, progress, a benefit – which suits the occasions it is used on. A warning is possible too.
Both predict. 必将 declares an outcome with confidence; 势必 reasons from a situation to what it will cause, and the result is usually a cost.
必将 is too grand for everyday plans. In speech, use 一定 or 一定会.