Hi HenryFullerton,
In Microsoft Teams, there are several ways we can join Teams meeting: join by a link, call into the meeting, and even join a meeting as a guest when you don't have a Teams account. However, no matter which method is used to join the meeting, attendees need
to receive the require information (the join link, the dial in number) to join the meeting.
For your reference: Join a meeting in Teams & Join
a meeting without a Teams account.
That's say, if you want attendees to join the meeting, you can invite insider people during the meeting by clicking on the ‘Show Participants’ icon on the call toolbar in the meeting, and click on the ‘Invite someone’ text box and start typing their name
to invite them.
Moreover, if you need to invite someone from outside your organization, click on the ‘Copy Join info’ button next to the invite text box and you can send the join information to outside attendees via email so they can join the team meeting.
Best regards,
Jennifer