Even though the language in Julius Caesar is considered to be pretty straightforward, reading Caesar (or any one of Shakespeare's plays) can feel like reading a really long poem. That's because Shakespearean drama is written in a combination of verse (poetry) and prose (the way we talk normally).
We break all of this down in the paragraphs that follow, but here's what you should remember about Shakespeare's plays. The nobility and other important figures tend to speak in "blank verse," which is formal. The commoners, or "everyday Joes," tend to speak like we do, in regular old prose. (Note: The play Richard II is the one exception to this rule – it's the only Shakespeare play written entirely in verse. Even the gardeners speak poetry.)
OK, so now let's look at Julius Caesar specifically.
In Julius Caesar, the noble Romans mostly speak in unrhymed "iambic pentameter," also called "blank verse." Don't let the fancy names intimidate you – it's pretty simple once you get the hang of it.
Let's start with a definition of iambic pentameter. An "iamb" is an unaccented syllable followed by an accented one (sounds like da DUM). "Penta" means "five," and "meter" refers to a regular rhythmic pattern. So "iambic pentameter" is a kind of rhythmic pattern that consist of five iambs per line. It's the most common rhythm in English poetry and sounds like five heartbeats:
da DUM da DUM da DUM da DUM da DUM.
Let's try it out on this line:
to CUT the HEAD off AND then HACK the LIMBS
Every second syllable is accented (stressed), so this is classic iambic pentameter. Since the lines have no regular rhyme scheme, we call it unrhymed iambic pentameter, or blank verse.
Not everyone in the play speaks in verse. "Everyday Joes," as we've said, don't talk in a special rhythm – they just talk. Check out the Cobbler's smart-aleck response when a nobleman asks him about his profession:
[...] but withal I am indeed, sir, a surgeon to old
shoes; when they are in great danger, I recover them. (1.1.5)
Notice here that, even though the Cobbler doesn't speak in iambic pentameter, he's still a witty guy – he cracks a joke about what he does for a living. This kind of clever and silly banter reminds us of some of Shakespeare's "clown" figures, like the Dromio twins in The Comedy of Errors and Speed in Two Gentlemen of Verona.