In Act 1, Scene 3. Casca is talking about the storm he had seen. Casca said, "But never till tonight, never till now, Did I go through a tempest dropping fire." (III:iii:In 833). So does this mean something bad is about to happen? Casca hadn't ever seen a storm this bad. He has seen seen would be split by a storm but never a storm that drops fire. Cicero was wondering what, why Casca was seeing this storm and why it was happening.
Act IV: Sc 1
In Act 2, Sc 1, Brutus thinks there is only one way to get Caesar out of the spot and center of attention is by killing him. Brutus says "He only wants to be crowned" (II:i:841). Brutus thinks Caesar wants to be in charge of Rome and that people want Caesar to be crowned. But Brutus doesn't want him to be crowned because he thinks there is a bad side of Caesar that Caesar isn't showing.
Act V: Sc
In Act 3, Sc 1, Caesar was saying "The ides of March are come." (III:i:861) and the soothsayer was warning him by saying, "Ay, Caesar, but not gone yet." (III:i:861) He is pretty much saying nothing is happening like it was supposed to. He gets warned and told by many people to read this and he ignores it. He also was being rude to all the people and saying stuff that he probably shouldn't and just listened to them.
THEME Act V: Sc v
In Act V, Scene 1, Antony, Octavius, and Lepidus think the only thing they can do to get back it to kill more people. Octavius said to Lepidus, "Your brother has to die too." (IV:i:884). Lepidus did agree and they are going to kill his brother. Later into it Antony was saying stuff like he is going to use Lepidus just to kill people and then get rid of him.
In Act 5, Scene 3, Cassius sent Pindarus to go check on Titinius over on top of the hill. Pindarus brought back news for Cassius. He said "Titinius is enclosed round about with horsemen, that make to him on the spur." (V:iii:In 27-28). But then Pindarus didn't realize Titinius was talking to Brutus and they were celebrating. So Pindarus helped kill Cassius and then he ran away when he realized Titinius was still alive.
In Act V, Scene v, Brutus has found out his friends have died and he knew him and his soldiers had to be strong to be able to defeat Antony. Brutus wasn't strong and I know because Brutus says, "Farewell, good Strato-Caesar, now be still: / I killed not thee with half so good a will." (V:v:In 50-51). I think the theme is Don't listen to other people and find out for yourself and don't kill yourself over people dying just get threw it.