Except is usually used as a preposition or conjunction, which means not including.
For example: "I teach every day except Sundays."
Expect is a verb, which we use when we think something is likely to happen, or someone is likely to do or be something in particular.
For example: "No one expects the Spanish Inquisition."
!Note - except is usually a preposition, but in rare circumstances except can be used as a verb.
For example: On a road sign: "No entry, buses excepted."