Hover your mouse over the video display area to see the control panel below and use the mute option (highlighted) to keep your mic muted until you wish to speak.
You may use the video icon to the left of the mic mute button to "mute" your video temporarily.
Teams attempts to only pick up your voice, so for smaller meetings you may not need to use your mic mute button.
But when on a large group conference or if you are in a windy or noisy environment, or simply not planning to speak for a long period of time, please use the mute option to keep your mic muted until you wish to speak. This will help reduce noise for other participants.
If your microphone is making too much noise, the host may mute you and you may need to check to see if you are muted and unmute yourself before your next contribution.