going to

I am going to buy a new car.

Going to is not a tense. It is a special structure that we use to talk about the future.

The structure of going to is:

subject + be + going + to-infinitive

The verb be is conjugated. Look at these examples:

subject be not going to-infinitive  
I am   going to buy a new car.
I 'm   going to go swimming.
He is not going to take the exam.
It is n't going to rain.  
Are you   going to paint the house?

How do we use going to?

going to for intention

We use going to when we have the intention to do something before we speak. We have already made a decision before speaking. Look at these examples:

In these examples, we had an intention or plan before speaking. The decision was made before speaking.

going to for prediction

We often use going to to make a prediction about the future. Our prediction is based on present evidence. We are saying what we think will happen. Here are some examples:

In these examples, the present situation (black sky, the time, damaged car) gives us a good idea of what is going to happen.

Note that we can also use going to with be in other tenses, for example:
  • I was going to tell him but I forgot.
  • I had been going to fix the car for ages.