Terminator movies have always been about robots that disguise as humans go back to the past and kill someone. But this new movie takes the franchise into a new time, during the war against the machines. Basically the movie is about John Connor's (the leader of the resistance) fight against the machine. Without spoiling it too much, he basically have to save his own dad, Kyle Reese.
Those who have seen the first three movies will know who John Connor, Kyle Reese, Skynet and a couple of characters in this 4th movie. The new character, Marcus Wright, is okay, but he was sort of a staple (to the Terminator franchise) character. It was nice to see more machines other than the humanoid Terminators, like there's the Hunter-Killers -flying machines that hunt and kill humans, this humogous biped robot that can deploy smaller, motorbike-like Terminators and the machines from Terminator 3. The humans or Resistance in this movie were more organized and have more access to military hardware than shown in the first two movies, then again it was still early in the war.
Chrisitian Bale in this movie used his Batman voice, there was one scene that I wished he yelled "WHERE IS HE?" like he did in The Dark Knight. But, Bale did an okay job portraying John Connor but his Batman voice made him as if he was still playing Bruce Wayne. Another thing I don't get is why Skynet made humanoid terminators that wield human weapons, while they made gigantic biped robots and huge flying machines, that makes it look silly. They haven't even fully made Arnold Schwarzenegger (oops, I guess I spoiled a bit of the movie) yet. Think about it, the machines that use human weapons are basically like "Beat me and get a prize". I could nitpick more but, I wouldn't want to ruin it for whoever is reading this.
If I were to compare this with another movie, I guess Star Wars Episode I comes in mind since this is a start of a trilogy, both being a prequel if you think about it.
Overall I give this movie a 3.5 out of 5
It is better that Terminator 3 but Terminator 2 will always be the best Terminator movie.