Chain link fences or corrugated metal sheets or panels at a height that has a survivable drop on the other side will not work. Thick walls or fencing at 25 ft. high isn't survivable on a drop. Illegal immigrants with the goal of breaking & entering are not experts climbers. Only free solo climbers can possibly climb the border walls/fencing free of anti climbing features.
Borders Walls are designed to funnel illegal border crossers to a gate, slow & stop illegals on their tracks. With an effective wall/fencing along with surveillance technology & ground patrols illegal crossing will be much more difficult to cross or penetrate than a barrier-less border. (The White House fencing & surveillance & armed guards, & Gated Communities works in this manner). Since Ancient times castle walls, border walls has serve to slow down or stop invading hordes for a time to buy time & ready their defenses against the impending hordes.
The great wall, wall guards, wall stations (bases) & signal towers couldn't be penetrated that's why Genghis Khan Had to go through or was funneled to east inner Mongolia where there was no wall. The Mongols where Superior Warrior & Tacticians, Eastern Europeans & Persians were no match against them as well.
Without a barrier tens of thousands can cross at the same time every minute. Walls prevents tens of thousands from braking & entering (invading) at the same time every minute.
The incentives for illegal crossing is fraud. Unaccompanied minors (teenagers) will get welfare & housing with clubhouse amenities. Anchor babies will get welfare/housing assistance. Accompanied minors will get welfare as well. Illegals use false identities & fraudulent social security numbers.
American citizens engaging in welfare fraud or any fraudulent schemes gets charge & imprisoned, but illegal aliens get sanctuary, especially the criminal element as they are not deported.
Before Lyndon Johnson's Presidency vetted Legal Immigrants came for work opportunities & only real refugees were seeking asylum, there was no refugee act at the time. Lyndon Johnson's great society programs initially was for U.S. citizens, as it expanded with various duplicate programs, illegal immigrants with minors & anchor babies are now being covered to overwhelm the school & welfare system.
In the middle east & some Asian/South Asian countries, illegal aliens engaging in capital crimes (rape, murder, smuggling/trafficking (drugs/human), grand theft & robbery) gets executed. Illegal alien gangs robbers/murderers were executed in a middle eastern country using cranes to lift the executed bodies in display for the public.
Until Birthright citizenship, employment opportunities, & welfare/housing benefits are abolished & denied to Illegal Immigrants the way Jordan's current policy is, a barrier wall is necessary. Only real refugees escaping genocides seek refuge in tenth cities Jordan will only provide