'Understand Endtime Signs'
Rev 1-3 is the vision given to John at Patmos concerning the spiritual conditions of the 7 churches then, which as individuals or a combination of churches represent the spiritual conditions of every church since. Rev 4-9 is the scene in heaven then, and the visions given to John concerning the 7 seals and the plagues of the 6 trumpets (bowls/vials) of the last days.
Rev 10 - Event in Patmos
Rev 10:1-3 I saw still another mighty angel coming down from heaven, clothed with a cloud. And a rainbow was on his head, his face was like the sun, and his feet like pillars of fire. He had a little book open in his hand. And he set his right foot on the sea and his left foot on the land, and cried with a loud voice, as when a lion roars. When he cried out, seven thunders uttered their voices.
John was presented with a little book - the Royal decree from the King of kings of John's new mission that he must prophesy again. The seven thunders are the instructions from God on what John should prophesy - the message of the cross, the everlasting gospel, salvation of the Jews, God's plan for Israel, etc.
Rev 10:11 And he said to me, "You must prophesy again about many peoples, nations, tongues, and kings."
Rev 10:4 Now when the seven thunders uttered their voices, I was about to write; but I heard a voice from heaven saying to me, "Seal up the things which the seven thunders uttered, and do not write them."
When John heard these instructions, he was not allowed to write them down but to seal them up. Since Daniel sealed up all Endtime mysteries, then John's mission must also be during the endtime with endtime mysteries.
Dan 12:9 And he said, "Go your way, Daniel, for the words are closed up and sealed till the time of the end.
Note - we thank God that we are the last generation and living in these last days, and all these endtime mysteries are now opened to our understanding.
The Seventh Trumpet
Rev 10:7 but in the days of the sounding of the seventh angel, when he is about to sound, the mystery of God would be finished, as He declared to His servants the prophets.
John will be serving during the period of the wrath of God (7 Trumpets) and has to complete his mission before the sounding of the final trumpet by the 7th angel, which will then herald in the Millennium Rule of Jesus on earth.
Rev 12:15 Then the seventh angel sounded: And there were loud voices in heaven, saying, "The kingdoms of this world have become the kingdoms of our Lord and of His Christ, and He shall reign forever and ever!"
Rev 10:9 So I went to the angel and said to him, "Give me the little book." And he said to me, "Take and eat it; and it will make your stomach bitter, but it will be as sweet as honey in your mouth."
Since John has obediently accepted the commission (taking the booklet), God will give him full authority and great powers, including the services of angels, to overcome the devil and his cohorts, etc.
sweet as honey in my mouth
When John perform his mission (eating the word of God), he will be so delighted and joyful (sweet in the mouth) to find that nothing is impossible, with many miracles similar to our Lord calming the storm.
my stomach became bitter
John's mission is painful (bitter) to see all mankind, who had taken the mark of the beast and left behind at Rapture, in excruciating pains during the wrath of God.