There are a few reasons why a Martini should be served with olives:

In the early days of cocktails, in addition to fresh fruits/berries and peels, bartenders would use whatever well-preserved food they had on hand as a garnish, including nuts, olives, and cherries thrown into the drink.

With experience, bartenders realized that olives or onions were a better match for a drink as crisp and flavorful as a Martini, and this practice became a permanent fixture, which is why the Martini is served with olives.

Expanded:

Other garnishes for martinis

1. Orange garnish

Garnish cocktails with orange fruits, which are a material that has a lot of different uses. Can be as simple as a piece of fruit on the rim of the glass, you can also try spiral skin, kumquat lilies and other complex decorations. Choose fruit that is firm, thin-skinned, intact and preferably unwaxed.

Wash the fruit first. Orange ornaments, mainly made from oranges, lemons and limes. Others such as pomelo, grapefruit, small mandarin oranges and satsuma oranges are also good choices. A simple drink can be made intriguing by using the peel to cut out little stars and floating them on top of the wine.

2. Miscellaneous Fruit Garnishes

Garnishes used in cocktails are meant to accentuate the look, not hide it. Fruit is seasonal and may not be in season, a bunch of fresh red currants hanging on the edge of the glass, or grapes dipped in frosting can be a garnish.