An email broadcast allows you to send multiple emails to contacts and use mail merge tags, as well as templates, to personalize your correspondence.  Note: An email broadcast functions like a Bcc and will hide the names of the recipients.

To use email broadcast, select the contacts that you would like to send the email to, go to Bulk Actions > Send an Email, and choose the message type of “Email Broadcast”:

From there, you can compose your email broadcast, provided you are within your email provider’s daily sending limits. For limits, please refer to other articles in our knowledge base.

You should be able to select "Insert Mail Merge" on the email draft screen shown in the screenshot above to pull the contact's first name into the email. This will ensure that each recipient of the email will see their own first name in the email.