Hello {studentfirstname},
I’m (your_name) and I work for (company_name). On (Career_fair_date) at (time), (company_name) will be joining your schools virtual career fair. We’d love for you to virtually attend as well and introduce yourself to some of our team members. 
We’re currently looking for students in the (preferred_field) field and thought you could be a good fit. If you would like to learn more about the opportunities at (company_name), our team would love to talk to you.
As we search for the best talents to join our company, we hope you consider (company_name) in your job search. Hope to (virtually) see you soon!
Best,
(your_name)