The E-class vowels make some variation of the "e" sound in English. They are:
אֶ
A segol is a short vowel and is pronounced as the e in met.
אֵ
A sere is a long vowel and is pronounced as the "ey" in they.
נֵי
A sere-yod is a long vowel and is pronounced as the "ey" in they.
אֱ
A hataf-segol is a very short or reduced vowel and is pronounced as the e in enemy.