I sometimes float, at times I don't,
They do both
Some people like me, some don't.
When they give disease we hate them, when given in vaccines we like them (some hate that too :D)
Millions see me, millions don't,
They are visible to many organisms, and invisible to many
Let me be upfront, I'm not any kind of boat.
Almost everyone has seen me at least once in their lifetime,
Everyone gets vaccine has seen them.Then there are many examples like rotten food, feces etc
Mind you, I only arrive if I'm given some time.
They take time to gestate and in proper conditions
Don't give me too much time else my host will evolve,
They affect their host: in humans positive and negative effects are there , they rot food etc
If you want my host you definitely should resolve.
I didn't understand this sentence much, one explanation is to save the host (food/animal/human) one needs a solution (resolve)
If you don't like me, throw me out,
Anything which has bacteria growth and is not liked is thrown out.
if you don't I'll spread out.
We all know this and have experienced this :D