Can I use Microsoft Teams to work with people outside my company?

Yes! Invite people to read files or even participate in creating the content. You can also invite external parties in Teams and/or Channels to become part of your productivity. You can determine what they can do in your environment (read, create, take control). As a company, you can influence whether or not you want this. In the Office 365 Compliance overview you can see which data is available to whom.