As you are probably aware the Systematic (IUPAC) name for methandrostenolone is
(8S,9S,10S,13S,14S,17S)-17-hydroxy-10,
13,17-trimethyl-7,8,9,11,12,14,15,16-
octahydro-6H-cyclopenta[a]phenanthren-3-one
While the chemical formula remains the same:
C20H28O2
Of primary importance is the process utilized to make methandrostenolone c17 alpha alkylated. Thus the 17th carbon molecule is altered to allow first pass through the liver. Now of course carbon bonds are covalent. Further more carbon bonds can have alkenes or double bonds, or alkynes which are triple bonds.
An sp2 hybridized orbital and a p-orbital that is inert with regards to the hybridization are what is used to from a double bond. Conversely an sp hybridized orbital and two p-orbitals are used for a triple bond from each atom. Thus the use of the p-orbitals to form a pi bond is basic logic.
Now that the basic explanations are covered lets dive a little deeper. This is where it gets tricky due to catenation (Thank god this usually is only used with carbon). The alteration of the c17 has differing effects. In some cases it comes out tertiary. The original formula introduced by John Ziegler was of course quartenary. Now this differentiation causes changes in the p-orbitals and sometimes engages previously inert p-orbitals to take a part in hybridization. Thus causing metandienone.