Md. Code, Transportation § 13–201

(a) In this subtitle, “perfected”, as used in reference to a security interest, means that it is valid against third parties generally, subject only to specific statutory exceptions.

(b) This subtitle does not apply to or affect:

(1) Any lien given by statute or rule of law to a supplier of services or materials for a vehicle;

(2) Any lien given by statute to the United States, this State, or any political subdivision of this State;

(3) Any security interest in a vehicle during any period in which the vehicle is inventory held for sale or lease by a person or leased by that person as lessor and that person is in the business of selling vehicles;

(4) Any lien arising out of an attachment of a vehicle;

(5) Any security interest claimed on proceeds, as that term is defined in Title 9 of the Commercial Law Article (Maryland Uniform Commercial Code -- Secured Transactions), if the original security interest did not have to be noted on the certificate of title in order to be perfected; or

(6) Any vehicle for which a certificate of title is not required under this title.