Look, English isn't so difficult. Take a simple word, like lead. It rhymes with read. Now, the past form of lead is led. It rhymes with the past form of read. But the past form of read isn't red, that's a colour. It's read, but it's pronounced like led. But if you pronounce lead like read, that's a metal. So read is like lead, read is like led, and red is like lead.
Now it's important not to pronounce leader as ladder, because it will sound too much like leather. Leader is pronounced like reader. Read is pronounced like bread, and read is pronounced like breed, which is similar to breathe, but not similar to breath. Breath is similar to breast, but breast isn't like least, it sounds like lest. It's important to note that like more becomes most, less becomes least, not lest.
You might ask, is reed pronounced read or read? The answer is read of course, the one that rhymes with greet. Greet doesn't rhyme with great. Great rhymes with grate, but meat doesn't rhyme with mate. Meat sounds like meet, which rhymes with greet. Meat also rhymes with meal, and so does mate with male and tale, which sound like mail and tail.
I'd also like to point out, that slay rhymes with pray (also with prey), but slayer doesn't rhyme with prayer. Also, depending on your dialect, this post might not make sense at all, because it's also a rule that you can basically pronounce things however you like, the only thing you can't do is use less where it should be fewer, that's a capital (not capitol!) sin, and you will be hanged (not hung!) for it.
