In most Islamic schools of thought, the Nikah is not valid without the essential role of a wali. Only the Hanafi madhab allows nikah without the presence of the wali, which you can learn more about here. Wali translates to protector, and some Muslims use the word to describe an Islamic saint. A wali is most often a paternal male relative who is in charge of the bride’s life before marriage. The wali must ensure the well-being of the woman in all aspects of her life; before and during the marriage process. In circumstances as important and life-changing as marriage, it is significantly beneficial for a bride to have assistance from a trusted individual; like her Wali, to settle on the best and most qualified man to be her husband and lifelong partner. A wali should be thorough in evaluating the woman’s future husband in an unbiased and purely intended manner. After the marriage, the responsibilities of taking care of the woman are lifted off the Wali and the husband becomes responsible for his wife’s well-being.
The majority of scholars agree that the wali must be a Muslim. By default, the father of the bride is her wali, however, in certain circumstances where the father is unable to be present as a wali, the role of the wali is usually taken on by the next closest mahram. The most common sequence of the role of the wali after her father is her paternal grandfather, son, grandson, brother, paternal half-brother, and paternal uncle. In a situation where none is available, then the Qadi (Islamic Judge) would assume the title of the wali, or any other righteous relative. The role of the wali is to consent to the marriage and assist the bride during the Nikah. Nikahnama provides an optional space for the wali’s signature on it’s marriage contract texts.