It's very unlikely the container would be ANY alloy containing tin. If it's truly aluminum, I would be concerned with aluminum toxicity, which is a concern in soils when pH drops much below 5.5. Though container soils are usually so low in aluminum that lower pH levels associated with most container media usually don't create a toxicity issue, they would if the container was made of Al.

Al

You've expressed thoughts about how hot it is in the area, so using metal containers for plants seems to me going directly against what the plant needs.

Some plants like it hot...with 8 hours and more of sun.
Roses for example.
Roses can do very well in containers as long as there is sufficient soil underneath to accommodate their roots.
A trellis effect can be given them for a climber.

Morning glories....put the container near a trellis, a fence, a post, M.G.'s would climb in no time in such a sunny spot.

Small trees themselves can be given large enough containers to add something to a sunny spot. As long as the roots have enough under them, evergreens love the sun.

Any plant given such sun has to be given moisture they need, when they need it and the container MUST DRAIN.

Clay pots are usually very reliable for doing well by plants. They drain very well if you don't clog up the holes by putting nothing but soil in them. Put something between the soil and the drainage holes and when you water, water to drainage--dump the excess.

You speak as though you have ideas of planting a tree as a permanent part of your landscaping IN A CONTAINER>
That is not possible given you live in a 5/6 zone.
Such a plant cant be left there through a northern winter and the soil and roots would surely freeze solid.

There are methods by which such containerized plants are left in the container and the container is buried wholly in the ground.
Your reference to a TREE speaks of something far larger than what one would think to move around.
If you have thoughts of producing shade for the area, give careful consideration to putting the tree IN THE GROUND...not in a container.
For that, the tree should be one that fits the area, provide shade sufficient for your wishes and not be a hindrance to the enjoyment of the area. Wanting shade is one thing, planting the wrong kind of tree is another.