The memoir class replicates the functionality of many independent packages, so if you are transferring LaTeX source from other documents using the article class, you may encounter some warnings or errors. The memoir documentation has substantial information about the packages it emulates, and the packages for which it provides equivalent functionality. See Chap. 18 Sec. 24 of the memoir manual for details. Quoting from the manual:
At the time of writing the emulated packages are: abstract, appendix, booktabs, ccaption, chngcntr, crop, enumerate, epigraph, ifmtarg, ifpdf, index, makeidx, moreverb, needspace, newfile, nextpage, pagenote, patchcmd, parskip, setspace, shortvrb, showidx, titleref, tocbibind, tocloft, verbatim, and verse. As well as the emulated packages memoir provides functions equivalent to those in the following packages, although the class does not prevent you from using them: fancyhdr, framed, geometry, sidecap, subfigure, and titlesec.
The Memoir Class 10th impression, 2015, p.345