if i took out food from a freezer and left it to melt and then put it in a microwave, is it contaminated or safe to eat?

thawing something doesn't 'contaminate" it...contamination indicates the introduction of a foreign substance. thawing wouldn't do that.
As to safety, it would depend on how long it sat out till it was thawed and exactly what it was.

The only "food" I can think of that would melt would be something like ice-cream or sorbet. Once melted, you couldn't "eat" it as it would be a liquid.

The process of melting doesn't in itself "contaminate" something but food could be "contaminated" depending on where you left it and what was put with it. I can't see how putting it in a microwave would make any difference one way or another.

Maybe you'd like to explain?

I do it all the time and I am ok

I do it all the time and I am ok

yes, it is contaminated! yes, it is safe to eat! Defrosting food before microwaving, frying, baking, roasting or grilling doesn't automatically mean it is not fit to cook and eat. I take food out of the freezer every morning for the lunch and dinner meals! I defrost them then cook them! That is the way food is prepared for a large family! We rarely eat out and when we do it is always some special occasion.

It depends on:

1. What food it is
2. How hot it got in the microwave
3. How long before you ate it
4. What bacteria are floating around

I do it all the time and I am ok

It depends. It's unwise to defrost at room temperature. You should either defrost overnight in the fridge or cook from frozen if labelled as such. Some foods will grow pathogenic bacteria in a short time at room temperature and as microwaves tend to cook unevenly there may be a risk of food poisoning.