system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What can a US president really do, can he build a wall? Offer free health care for all?

Without the help of the Senate, can the US president really do anything at all?

For example, build a wall between Mexico and the US? Ban a certain group of people? Create free health care for US citizens?

Or, putting it another way, regardless of who is elected to the white house, the Senate could still order a wall to be built, or offer free health care.

So, in the end, does it really matter who is ultimately 'in charge'?

I understand he can *propose* a law, (or can he?), but that could be laughed at by the real law-makers, (or even the constitution court).
gpt
This is a very complicated question, and in some ways the answer isn't even certain. The simplest answer is that the president has *The Executive Power,* and all that it entails.

At an ELI5 level, the U.S. President has a number of straightforward powers, including:

- **The power to veto laws** - It the President does not a agree to a bill passed in Congress, it does not become a law (and thus is not legally binding) unless Congress overrides the veto, which requires supermajorities in both houses of Congress (which are hard to get).

- **Command over the armed forces** - The President has the final authority over the military, and serves as the ultimate decisionmaker for military strategy and action. 

- **The Pardon power** - The President can pardon someone convicted or accused of a federal crime.

- **The Appointment power** - The president gets to nominate people for senior government positions, although Senate approval is needed for many positions. 

- **The responsibility to execute the laws** - The Constitution charges the president with faithfully executing the laws, which means using the departments of government to ensure that the will of the legislature (and thus the people) as expressed in law is carried out.  This covers everything from making sure people are prosecuted for crimes to keeping the parks open. It also covers things like "executive orders" where the President makes a policy that governs the behavior of government officials and employees (other than those that work directly for Congress, the states, or the executive.)

There are some others as well, like representing the U.S. abroad, and "executing laws" has expanded considerably after Congress created agencies that have a lot more power that is delegated to the agency or the president to use to make and enforce regulations.

The complexity comes in because Congress has power to, and many of those powers are somewhat open ended. 

So, take the wall.  If the Congress doesn't give the president money to build the wall, then he can't build it.  But what if the president orders the military to build the wall --since he's the commander in chief?  Can he repurpose the money? Can Congress pass a law saying the money for the military can't be used that way?  and on and on. 

Likewise, the President has tremendous power over diplomacy, but banning a religious group might be unconstitutional, so it's possible that the ban could be ordered, but the Courts would overturn it -- raising the question of who would enforce that ruling (since that's the executive's job). 

As a result, some of those questions don't have definite answers, just likely ones.