The first movement opens with the four-note motif discussed above, one of the most famous in western music. There is considerable debate among conductors as to the manner of playing the four opening bars. Some conductors take it in strict allegro tempo; others take the liberty of a weighty treatment, playing the motif in a much slower and more stately tempo; yet others take the motif molto ritardando (a pronounced slowing through each four-note phrase), arguing that the fermata over the fourth note justifies this. Some critics consider it crucial to convey the spirit of and-two-and one, as written, and consider the more common one-two-three-four to be misleading.
The first movement is in the traditional sonata form that Beethoven inherited from his classical predecessors, Haydn and Mozart (in which the main ideas that are introduced in the first few pages undergo elaborate development through many keys, with a dramatic return to the opening section—the recapitulation—about three-quarters of the way through). It starts out with two dramatic fortissimo phrases, the famous motif, commanding the listener's attention. Following the first four bars, Beethoven uses imitations and sequences to expand the theme, these pithy imitations tumbling over each other with such rhythmic regularity that they appear to form a single, flowing melody. Shortly after, a very short fortissimo bridge, played by the horns, takes place before a second theme is introduced. This second theme is in E flat major, the relative major, and it is more lyrical, written piano and featuring the four-note motif in the string accompaniment. The codetta is again based on the four-note motif. The development section follows, using modulation, sequences and imitation, and including the bridge. During the recapitulation, there is a brief solo passage for oboe in quasi-improvisatory style, and the movement ends with a massive coda.