A metal whisk is a kitchen tool made of thin wires that are looped together. It is used to beat, mix, or whip ingredients like eggs or cream. Full definition
Pour hot water over matcha and whisk using a small metal whisk very fast for 30 seconds (try to get some bubbles!). (rachelmmolenda.com)
I don't have a shaker, so just weigh the dry ingredients into a plastic beaker, add water, and mix with a small metal whisk. (myprotein.com)
Lemon juice may react with other utensils, for example, if you are using a pan that contains any aluminum or using a metal whisk. (flavourandsavour.com)