My LG over the range microwave makes a rattling noise when I am cooking. The sound is not there is the item I am microwaving is heavy.

All microwave ovens have microswitches to confirm door open/closed. Many have several, and a bad switch can cause all sorts of strange issues. My ovens have 4 such switches, and I've had several go bad. You have to open the oven up to see which you need, measure them, and replace the bad ones. The good news is that the switches aren't expensive.

Hi, the rollers on the support mechanism has residue, try cleaning the rollers and the track it follows, should resolve the sound problem

It's not a good idea to continue to use it when it's making an unusual noise.
It may be arcing, which can lead to further failure or a fire, or it may be a defective stirrer or fan ,which can lead to uneven cooking or further failure.
$360 for a service call? Are you in Alaska or on Mars? That's insane. Maybe you can contact another servicer in your area?

It's not a good idea to continue to use it when it's making an unusual noise.
It may be arcing, which can lead to further failure or a fire, or it may be a defective stirrer or fan ,which can lead to uneven cooking or further failure.
$360 for a service call? Are you in Alaska or on Mars? That's insane. Maybe you can contact another servicer in your area?

check to make sure the plate is inline with the roller setting so it rolls around inside correctly when in use, other wise that will rattle.

If the sound is a bit like angry bees but muffled, then the magnetron is on its way out.
Sorry.

Microwave works fine. During operation there is a rattle sound. The table moves correctly, only problem is the sooud of a rattle. It appears to be on the right side, lower area.

It can be a sign of dying magnetron and possible damage to the microwaves chute. If the chute is damaged then the microwave is not repairable. Check the manufacturer warranty on the magnetron.






The failing transformer will cause a deep "growling" noise; the failure of the magnetron will sound more like a sizzle.

Popcorn is heated by a metallic insert in the bag. This causes some additional power consumption by the magnetron. It is no cause for alarm.

In order to try to set your mind at ease I will have to explain the Basics on how a Microwave Oven Functions.
When a Microwave Oven is set to COOK ...START. It cooks at 100%. There is no lowering of the heat as with a Range ( Cook Top) Control. So in order to do the other things such as DEFROST, WARM, or anything other than 100% COOK. A COOK ON- COOK OFF system was utilized. To DEFROST, the Microve COOKS at 100% for 30% of the TIME, then IDLES for 70% of the TIME. COOK ON 30% of the TIME, COOK OFF 70% of the TIME = DEFROST This is why you can hear the CYCLE. More power is required during the ON CYCLE, thus the lower vibration. The Vibration occurs when the High Voltage Transformer is turned ON ( COOK ON).
The VIBRATION seems to have got louder with age. This is somewhat normal as there is a vibration from the High Voltage Transformer present every time the Microwave is used. screws and other metal parts seem to get loose with this vibration. There is no solution, unless you can tighten EVERY screw, nut, and bolt in the unit.
Sorry!