From the beginning until 0:14 is the introduction, which sets the tone with continuous repeated strings. At 0:14, the melody is presented through the strings, with brass keeping time. As the melody progresses, John Williams often uses high percussion and flute to add extra decoration. Whether it's the brass, winds, or strings with the melody, there is always a group of instruments keeping the tempo with repeated eighth notes. At 2:56, Williams changes things with ascending trumpet runs that lead into the conclusion.
For my pop song, I choose to analyze We Are Young by Fun.
From 0:00-0:08 is the introduction. The intro sets the rhythm with the beating of the drum.
From 0:08-0:40 is the first verse.
From 0:40-0:49 is the pre-chorus. Lyrically as well as rhythmically, this sets up the chorus.
0:49-1:30 the chorus returns.
From 1:30-1:51 is the second verse.
2:32-3:14 is the bridge. It is used to offer some variation to the chorus and verses. It is characterized by the layered nananana na na in the background.
3:14-3:55 is the chorus again.
Finally, from 3:55 to the end is the conclusion. The beating background drops out and it's left with only the voice and piano.