If you already have a Will, be aware it will automatically be cancelled by your marriage. It is assumed that your wishes will have changed as you now have a husband or wife to take into account, and if you do not make another Will then you die intestate, and certain rules as to who inherits will apply.
It is possible to make a Will in contemplation of your marriage - but advice needs to be taken to ensure that this Will would be valid.
If you have children from a previous marriage, it is possible to draw up a Will making provision for your new husband or wife for the remainder of their life, but ensuring that after their death the assets pass to your children. You will need a solicitor to help you do this.