In almost all circumstances, a married couple should have two separate wills. There is the option of a “joint will” but in practise these are very rare and are treated as two separate wills by the courts anyway; the will is submitted for probate when the first testator dies and then again for each other testator.
With a pair of wills, each individual can specify how they want their possessions to be divided, which offers much more flexibility than a joint will.
A change in your marital status is an important point at which to write or update your will, as getting married automatically revokes any existing will, unless that document specifically states otherwise. This means that you will be left intestate and, in the event of your death, your estate would be distributed according to the laws of intestacy. Be sure to make the will after you get married and not before, otherwise it will be invalidated.
It is also very important to update your last will and testament if you separate from a spouse or civil partner. Under current laws, if you are in the process of getting divorced, your spouse remains first to inherit under the laws of intestacy until the decree absolute is issued. If you have a will in place, your spouse remains entitled to the share specified in the will until the point at which the decree absolute is issued, after which they are treated as if they died on the day at which that decree was issued.
The only way to ensure your possessions go to those who matter to you is to have a valid last will and testament in place. Make a will now.