Can you put heavy things on artificial grass?

Yes you can. The question becomes for how long before you make a pressing mark on the lawn. Remember seeing some carpet pressing leg marks after you move a heavy furniture? You will see the same if you put heavy things on artificial grass. So by putting heavy things on turf, you won't hurt or damage the product itself only that you have to be aware the pressing marks left by the heavy things after a while. The difference between artificial grass and carpet is that artificial grass fibers have their own "memories", after a while being pressing down by heavy things, the fibers will remember that and will keep down. Depending on how big the areas of laying down grass, you might find it difficult to get the fibers back up blending in with the rest of the fibers naturally. If for a small section, you can always use a hair dryer to heat it up a bit and press the fibers to directions along with the rest, but I don't think it would be an easy job to work on fibers on a large scale. So whatever you are planing to put onto the artificial grass, always give some good thoughts and plan well and knowing that you will see the pressing marks on the grass after you move the heavy things. Again, by putting heavy things onto artificial grass won't damage the turf.