Microsoft has released Guest Access for Microsoft Teams, but Microsoft Teams guest access is a tenant-level setting and is turned off by default, so i will show you how to turn this on.

Turn on Guest Access on tenant level

Go to your Admin portal, Settings, Services and Addins and select Microsoft Teams. Or use the link below.

https://portal.office.com/adminportal/home#/Settings/ServicesAndAddIns

Invite guests to your Team

go to your Team you want to share and insert the guest users email address