As pointed out, it is Gabriel's job to bring the message from God to the prophets, who then deliver it to the people. This because the human mind is not strong enough to see God directly (I don't know if that makes sense, but the following verse should make it clearer)
The Elevated Place (7:143)
When Moses came to the place appointed by Us, and his Lord addressed him, He said: "O my Lord! show (Thyself) to me, that I may look upon Thee." Allah said: "By no means canst thou see Me (direct); But look upon the mount; if it abide in its place, then shalt thou see Me." When his Lord manifested Himself to the Mount, He made it as dust. And Moses fell down in a swoon. When he recovered his senses he said: "Glory be to Thee! to Thee I turn in repentance, and I am the first to believe."
But even seeing Gabriel was quite a shock for the prophet Muhammad. As the following story describes:
*For the moment, however, he was as if a man pursued. As he descended, he heard a great voice crying: ‘Muhammad, thou art the Messenger of God and I am Gabriel.’ He looked upwards, and the angel filled the horizon. Wherever he turned, the figure was there, inescapably present. He hastened home and cried to Khadija: ‘Cover me! Cover me!’ She laid him down, placing a cloak over him, and as soon as he had recovered himself a little he told her what had happened. The Prophet was in fear for himself. * source
I hope that answers your question :)