Meringue is delicious, but only if it's airy, fluffy and sweet, so add the sugar after you've added your eggs and started whipping. It's a simple technique to get the fluffiest meringue possible. Image from ruthanddave.
You might think that adding all the ingredients together before you whip the meringue is best, but Dana Cree, writing at Lucky Peach, explains why that isn't the case:
If you add sugar before the eggs are whipped into a foam, it will prematurely bond with the proteins and limit their ability to trap air. If this happens, your meringue will be dense as a marshmallow soup, if such a thing existed. To avoid this, whip the egg whites to full volume, trapping as much air as possible, until they increase to eight times their original size and hold medium peaks. Then, and only then, add your first small addition of ultrafine sugar.
You'll end up with lighter meringue by making this small tweak, and it will definitely be noticeable in your desserts. For more tips on improving your meringue, hit the link below.
How to Make Meringue [Lucky Peach]