Yes, aluminum foil is safe to use in the oven at most temperatures, and it can be useful for a variety of purposes:
Reflecting heat: Aluminum foil can help food cook evenly by reflecting heat.
Lining baking sheets: Aluminum foil can make cleanup easier when lining baking sheets.
Wrapping food: Aluminum foil can be used to wrap food or cover it to retain moisture.
Making packets: Aluminum foil can be used to make small packets for oven cooking.
However, there are some things to keep in mind when using aluminum foil in the oven:
Don't line the bottom of the oven
Lining the bottom of the oven with foil can cause problems, including starting a fire.
Don't use foil above 450°F
Some say that 450°F is the highest temperature you should use aluminum foil at, as food will likely burn before the foil melts.
Use either side
Unless you're using non-stick foil, it doesn't matter which side of the foil you use.
When not to put aluminum foil in the oven
Aluminum foil should never be used as an oven liner.
Aluminum foil can block vents when used as an oven liner, causing problems with airflow and heat distribution. Aluminum foil can also scratch the oven's enamel.
Aluminum foil should never be used when baking cookies.
Baking cookies on aluminum foil may result in uneven baking. Since foil is a conductor, any part of the cookie that comes in direct contact with the foil will bake faster and may burn the dough. Choose baking paper instead.
Aluminum foil should never be used in a microwave.
Putting aluminum foil in a microwave can damage your appliance or cause a fire. The U.S. Food and Drug Administration states on its website: "Metal pans or aluminum foil should also not be used in microwaves because microwaves reflect off these materials, causing uneven cooking of food and potentially damaging the oven."