Beethoven is widely regarded as one of the best composers of all time. I read an interesting passage in Leonard Bernstein's The Joy of Music where he breaks apart Beethoven's use of melody, harmony, rhythm, counterpoint, and orchestration and concludes that their either complete garbage or simply average. But Bernstein argues that what truly sets Beethoven apart from all other composers is his use of form, "the inexplicable ability to know what the next note has to be."
This symphony is also known as "Eroica," the heroic symphony. During the time it was written we find Beethoven in the depths of despair. Beethoven had written this masterwork with the (then) honorable Napoleon Bonaparte in mind. In fact, the piece was originally titled "Symphony No. 3, 'Bonaparte.'" But when Napoleon declared himself Emperor of France in 1804 Beethoven famously tore up the title page to his symphony and renamed it "Eroica" after the unnamed hero.
Eroica was completed not long after Beethoven wrote the Heiligenstadt Testament, which was a very revealing non-musical work about his worsening deafness. Can you imagine dedicating your life to music only to realize that you are slowly losing the ability to hear? Nevertheless, Beethoven had many more important musical contributions yet to come.
I personally like this symphony because of how it sounds, but I also like that some key facts about it are easy to remember because of the rule of 3:
Though written in 1803, the first public performance was on April 7, 1805 in Vienna. Today it is often performed and recorded by orchestras, giving you ample opportunity to find a favorite recording!
Symphony No. 3 in E Flat Major, Opus 55 - "Eroica"
I: Allegro con brio
II: Marcia funabre-Adagio assai
III: Allegro vivace
IV: Allegro molto