Weddings and receptions are occasions where you can wear intricate and heavy necklaces. But always think about the balance between everything, including the size and length of your necklace. If your dress has a round neckline, choose a piece of medium-sized jewelry that matches with the overall look.
If you are a guest at the wedding, do not exaggerate your jewelry. You can wear a locket or light pendant, but wearing an appealing necklace may not work as the entire focus would go to the necklace rather than the outfit.
If you are the bride, keep in mind that your necklace should primarily match with your gown. Wear a pearl necklace if you want to keep your look simple. Pearl necklaces are best if you want to accentuate your gown.