Lifting weights

Lifting weights is an exercise

Lifting weights = subject

builds muscles = predicate

it just means lifting weights that is not on a machine like using a curl bar

This answer depends on your diet. If you continue to consume the same amount of calories after you quit lifting, then yes you may get fat. Lifting weights burns calories and muscles need these calories to build more muscle. If you quit lifting weights, your body no longer needs as many calories. Also, your metabolism will slow after you quit lifting weights.

Now, if you quit lifting weights and also cut calories, you will not get fat.