Lightning Email Templates and Merge Fields

Hello,

I have created a lightning email template and wanted to use a few merge tags for a custom object called lead. When sending the email the spaces of where the merge tags should go are blank. 

For example, I am trying to use this:  {{{Lead__c.Name}}} 

Note: this field is a formula field

I essentially created this email template because it is used in a flow and the email will be sent when the owner of a record was changed.