The Wonderful World of Cliches, Metaphors, and Similes
Like most things in songwriting, cliches are a tool. It's up to the writer to use them well, or poorly, or not at all. To a certain extent, it's a matter of taste - personally, I don't care for them unless there's simply no other way to say what I'm trying to say. (Every day, I hear from publishers that they want something "fresh" - what that means is something relatable on a universal level, yet said in such a new and different way that it causes people to take notice.)
So what is a cliche, exactly? Dictionary.com defines it as something trite, or hackneyed, that has lost its impact from overuse. Strong as an ox. Dumb as a bag of hammers. A chip off the old block. A dark and stormy night. There are thousands of them, and a quick Google search will turn up plenty. If I have to use them, I try to turn them on their head or take a slightly different angle. Everyone has heard "doesn't have a snowball's chance in hell". But how about changing hell to, say, Florida? Then you're taking something well worn and making it a bit fresh.
A simile is a comparison of one thing to another- "sharp as a tack", "blind as a bat", etc. These are slightly more useful than cliches, because they can help build an image in the mind of the audience, provided they are used in a different way. For example, instead of saying "I feel sad", you might say "I'm as sad as a rainy day". The line isn't great, of course, but it gives you an idea of how to paint pictures with your words using this tool. As with cliches, I would strongly advise against taking the well worn path unless there's either simply no other choice - it supports the hook, the lines around it somehow put the simile in a fresh light, etc.
Metaphor is a broader type of Simile - typically, a simile is a bit more narrow "You're a pretty as a flower". A metaphor might be something like "Don't count all you chickens before they hatch", or "Don't burn all your bridges". Even calling someone a "knight in shining armor" is a metaphor. Again, an excellent writing tool, provided the writer uses it in a unique way. So make new metaphors (or discover under utilized ones)! There is one additional pitfall to this tool, and something I see all to often in novice songwriting: mixing metaphors. "We burned that bridge before we crossed it" - confusing! How can you cross a bridge you burned? Or what about "Her lips were on fire, and it gave me chills"? Fire doesn't give you chills, it burns! Make sure you think your metaphor through - no matter how cool of a line it is, if it doesn't make sense, you're going to confuse the audience and they may miss the whole point of the song!