No they are not made of muscles. Glands are modified epithelial tissues. Glands are basically of two types Endocrine and Exocrine glands.
It is a gland that lacks a duct system. The secretions are directly
poured into the bloodstream. They secrete hormones through exocytosis mostly.
It is a gland with a duct system. The secretions(sweat, sebum,saliva
etc) are transported onto a surface of the body (e.g skin or lumen of GI tract) by
ducts.Exocrine glands may be controlled by muscles at the duct level.
There are three types of exocrine glands based on the process of secretion of chemical substance at a cellular level$-$
It is a gland in which the apical portion of the secretory cells are distintegrated to release the chemical. e.g- Apocrine sweat gland
It is a gland in which the secretory cells are completely disintegrated to release the chemical.e.g.- Sebaceous gland
It is a gland in which the secretory cells remain intact and the chemical is
released through exocytosis.e.g.- salivary gland